Hope this helps. My 25 year-old son and I just got back from a GTNP/YNP trip-
Here are some notes/bits of advice from trips with my wife/son/daughter to YNP & GTNP just about every other year since they were pre-teens, and now both are in their mid-late 20's, so about10-12 trips. Some of this is heavily geared to flyfishing, as my son and I did a fair bit, and then some is geared to day-hikes. Consider buying a "National Geographic Trails Illustrated #201" map-tear-resistant, waterproof, extremely-detailed, revised & updated every year or so, GPS co-ordinates, usually less than 15 bucks. You can get one for the Bridger-Teton Natn'l Forest and GTNP, also. Another suggestion, for the hikes, is "Day-Hiking in Yellowstone", by Tom Carter-in co-ordination with NatGeoTrailsIllustrated Maps-bought it for $5.95-it fits in your cargo or top shirt pocket. It has at least 20 hikes, from "short hikes/easy walks" to "long day hikes to overnight trips".
Suggestions for YNP fishing-
1. Just north of Tower Junction, take right onto the NE Entrance Rd that takes you to Lamar Valley, go maybe 1/2-1 mile over the "tall" bridge over the main Yellowstone River, to the Yellowstone Picnic area, hike 1/2 mile down along the east side of the Yellowstone, to where the Lamar joins from the east. Fish dries or nymphs at the junction, then walk upstream the Lamar, fishing pockets as you go. Good Cuttie action.
2. Park at Tower Junction, walk down the long stairway, walk south to the beach/bank of the main Yellowstone, walk about 300-400 yards upstream and start fishing the west bank, working dries behind the boulders. Again, eager Cutthroat action...and you can keep walking upriver for another mile if you want, just keep bear spray handy. We've not yet seen any grizzly along the main river...yet.
3. As you're on the NE Entrance Rd, when you get to the Slough Creek turnoff, park just past the bathroom, and there is a faint hiking/old wagon trail just off the road past the bathroom, bearing NW and WNW across rolling high plateau. Do NOT go all the way up to the trailhead or try to get to the "famed second meadow", unless you want to fish with crowds. Actually, easy walking WNW, and this will take you to where the final stretch of the "meadow" Slough Creek, with wolf and griz tracks along the bank, dumps down into a kaleidoscope of pocket water where rainbows and cutties will hit dries and droppers. So, you go from technical to almost "Tenkara" high-sticking among the boulders, fishing/walking as the water turns WSW until Slough Creek dumps into the Lamar River coming in from the south.
As for bear spray, I always buy two canisters for myself, and clip them on the right & left side of the chest-strap of my backpack. My son and I had one day, up in the NE corner, where we hiked in to fish Cache Creek, parking where Soda Butte Creek is on the south side of the road, walking across a little wooden bridge right at the parking lot. The hike in is all in the valley, and we often see mule deer and antelope. The cutties were hitting quite well. We saw five griz and one black bear, in one day, while fishing where Cache Creek flows into the Lamar. With all that crashing water, you won't hear them approaching, and there was fresh bear-droppings everywhere. We had a similar day on the Nez Perce, a smaller stream but with decent brown trout along the undercut banks, and we saw two females each with two cubs. The week after we left, a hiker who started at Merry Mountain, hiking the Nez Perce trail solo...was mauled and YNP personnel found half his torso...he had notified none of the YNP personnel that he was hiking solo, and there was no bear spray, but there were Snickers wrappers strewn about, and this was later confirmed by family members. That same summer, a husband and wife were hiking fairly close to the Tower Falls parking lot, along the rim, and they got between a grizzly sow and her cubs. Neither had bear spray, and the wife did not survive. The Nez Perce incident was "in the backcountry", but the Tower Falls incident was less than a half-mile from the parking lot.
My logic is that if one hand is on a flyrod or trekking pole, the second or two quicker that I get my left or right hand on a canister and pull the trigger, then I have less chance of becoming a statistic, and the extra $75, well I'm worth it, and so is my family. (BTW, if you do some serious hikes, purchase some trekking poles.) My son carried two canisters also, as we would get to fishing different runs. However, if everyone hikes together, I'd still get a minimum of two canisters. Also, if you do the mountain biking, don't forget the bear spray...in an initially unreported incident, in 2010-201, then leaked to the press, wolves have been known to track cyclists touring the Loop Rd of YNP, and in one incident the "problem alpha male" met his demise via YNP personnel's 12-gauge. I won't delve deeply into spray vs. handgun debate...but if you hit a griz in the heart 5 times with a (fill-in-the-blank) round, he/she still has enough circulation to breath and pump blood for another minute, enough time to chomp you...or you can expertly shoot him/her in the brain at 5 yards as they charge...or you can hit them with a cloud of spray, preferably both canisters, that shuts down their lungs/spasms their eyelids for 2-3 minutes, time for you to back out.
One other point...when old canisters expired... a day or two before we'd leave for YNP, I'd have my wife & kids READ THE DIRECTIONS on the expired can, then go out in the backyard (we have 4 acres), and practice and pull the trigger, while one of us videos it. We'd then review it. It's important to see how the column of spray comes out, and you spray it at the ground right in front of the grizzly. If they hit that wall of nuclear pepper spray, then bronchospasm and blepharospasm is immediate, they can't breathe and can't see, and if they can't breathe or see, they can't charge. Then you back out...or get out at whatever pace is safe without tripping or falling off a cliff.
Don't forget Jackson Hole and GTNP, or do that another trip. The tourist crowds are crazy, but the girls may like the people-watching and a little shopping. Jack Dennis Outdoors on the square for the male member(s), Snake River Angler and Dornan's in Moose WY...a bit of reviewing flyfishing gear and pizza for the girls...and a cold beer for dad. The National Museum of Wildlife Art is almost as stunning as the Buffalo Bill Hisorical Center, has an indoor/outdoor cafe with a commanding vista high above the National Elk Refuge and Flat Creek, and sits just north of the Bridger-Teton Visitor Center, which is a block north of town, and is a great resource for GTNP/YNP maps and they have a gazzillion volunteers that will give you the info you need and answer questions. Farther north, and at the NW corner of "The Hole", is the "new" visitor center for GTNP at the north end of the Moose-Wilson Rd, just past the overlook at a wetland where you've got a good chance of seeing moose-cows, calves, bulls. The visitor center was completed, I believe, in 2011, and is a great educational center. The drive along the very narrow Moose-Wilson Rd is cool, and the Rockefeller Education Center is great...but you gotta get there EARLY, as the parking lot is tiny...and the nearby day hike to Phelps lake is breath-taking...remember to bring Nalgenes or Camelbaks for the daypacks...and yes, there are griz there, also, but if you follow the NPS advice, you will be fine wherever you go. As you get out of the "narrow" section of Moose-Wilson Rd, on the southern end of the road, there is a great hike on the west side, at the Granite Canyon Trailhead, just about 3-4 miles north of Teton Village. Also, Westbank Anglers is on the Moose-Wilson Rd, on the east side about two miles south of Teton Village. For fishing GTNP, easy access to Swabacker's Landing on the Snake River, access is by driving north of the airport, north past Glacier Point View Turnout, on the west side of the road. Swabacker's Landing can be a bit tricky, depending on the flows and level of the Snake. Some other good day hikes are those to Bradley and Taggert Lakes, and Signal Mountain. Also, there is a great campground on the way to Kelly, WY...need to check availability...and the Gros Ventre River parallels the road...decent dry-fly fishing for Cutthroat this time of year, or a dry and a nymph. If you're coming to YNP from GTNP-
55 miles Jackson, WY to the J,D. Rockefeller Parkway, and 70 miles from JDR Parkway To West Yellowstone, MT. This will take four hours of driving...or longer.
127 miles Jackson, WY to Mount Washburn...remember the speed limit in YNP is 25mph majority of the Grand Loop Rd...this jaunt takes 4 hours, also.
Need waders or just do the wet-wading with good sandals or ltwt hiking boots you don't mind getting wet. Things dry quickly in the low humidity. Flies that work in GTNP/YNP this time of year, and the gear to consider...5wt 8.5' or 9' rod w/ floating weight-forward line and a 4x or 3x leader, barbless hooks,- Madam X, Turk's Tarantula, Willy's Winged Chernobyl, Chernobyl Ants, Hoppers-#4-8 size, even try size 10-14; consider Sofa Pillow sz 4-8, Elk Hair Caddis 10-14, PMD's 14-16, Adams/Gray Wulff, Royal Humpy, Para-Adams 10-12, Foam Beetle or Black Ants 14-16, Yellow Sally/Blonde Humpy/Yellow Wulff/Jay-Dave's Hopper 10-14. For any "dry & dropper" or drifting nymphs-Bitch Creek/Wooly Bugger 6-10, Beadhead Prince/Hare's Ear/Copper John/Pheasant Tail 12-16. If the girls are young enough, look at the YNP regs to see what streams they can fish with non-fly tackle, and/or "youth-only" areas. For sure, get a copy of the current fishing regs, and look at the maps as to which YNP streams are in "High Grizzly Activity" areas-Nez Perce Creek, for instance. The YNP Canyon Village flyshop personnel actually are very helpful when you need advice on what/where/when...and there is an office next door where YNP rangers can give advice about hikes.
For both fishing and non-fishing sights-Firehole Canyon is impressive, Firehole River and the bridge crossing. If you go over to West Yellowstone, Craig Mathews' Blue Ribbon Flies is a neat shop, they have a great website with weekly fishing report, and say hello to the dogs. There's also Bud Lilly's shop and Madison River Angler. There is/was a great little bookstore in West Yellowstone "The Bookworm", but since the owner is no longer with us, I don't know if it's still open. Speaking of books, for reading you may be able to order from Amazon, three books that my kids couldn't put down-first was "Hawk's Nest", then the other two were a bit more macabre-"Mark of the Grizzly", and "Death in Yellowstone"...accounts of how unprepared campers had less than healthy interactions with grizzlies and the various dangers of YNP-it's not DisneyWorld. There are good pizza places and one good Italian restaurant, great for tired families and the prices are reasonable. May also consider Bullwinkle's restaurant for decent tourist prices and food.
I agree, that if coming in from Cody, definitely stop and you'll need a full day or two to take in the Buffalo Bill Historical Center-it's as good or better than the museums at the Smithsonian. In Cody, Tim Wade's NorthFork Anglers is a great flyshop, that has bent there "forever", and they are very helpful. I also agree that the trip to/across Dead Indian Pass/Sunlight Basin is gorgeous.
If coming in from the North Entrance, Gardiner, MT is a small/dusty town without the amenities of the other "gate" communities, but has Park's Fly Shop, with good selection and good people. Plus, the Gardner Rvr flows parallel to the road north of Mammoth Hot Springs. This time of year the cutties hit well, and you might see antelope coming in, or bighorns on the hoodoos above and on the north side of the road, and you can probably count on the resident "yard/lawn elk" that hang out around the buildings at Mammoth, as they enjoy grazing the well-manicured grounds and lying in the shade of the buidlings. Good tent-camping at the Mammoth Hot Springs locale, and good shower facilities, and a hot spring in the Gardner River that is a "YNP-approved" swimming hole. Just watch out for some of the non English-speaking camera-carrying tourists as the Park Rangers grab them by the collar and pull them back from 10-feet away from the elk and/or bison. An entertaining sight.
Other sights at YNP are the groups of Harley riders, and the groups of road-cyclists...and bring your rain gear, good broke-in lightweight hiking boots, fleece tops and beanies, and/or windbreakers AND gloves, as wind can get fierce as you're glassing for grizzly and/or wolves in Hayden Valley or Lamar Valley, or up on Mt Washburn after you've made the hike, or even Elephant Head Mtn above Yellowstone Lake. It can get COLD and COLD/WINDY, so prep for warm/hot and cold/windy the same day. Yes, in July in YNP.
Coming in from the West entrance, the drive along the Madison River is pretty, then coming into Madison Junction you parallel the Gibbon River then make sure to get out and view Gibbon Falls. Of all the trips to YNP, above Gibbon Falls is the only place we've seen a mountain goat, a large billy. Then on to Monument Geyser Basin and Norris Geyser Basin, with sulphur all through the air. At Norris Junction heading north, then east along the Gibbon River criss-crossing under the Loop Rd, then finally to a beautiful area, Gibbon Meadows, and in this area is also Virginia Cascades, worth stopping and viewing. Gibbon Meadows is where you always see folks flyfishing, but the fishing here is really technical...but the meadows are gorgeous. This is one area where my wife and I photographed a pack of wolves on an elk kill. The lighting in the meadow is perfect, and we just happened to come on the spot, able to photograph with my tele lens from a "safe" 300 yards.
My opinion of "Inspiration Point" at the Upper Falls of the Yellowstone River is "get there early", or you will be smothered by the crowds. I find the Lower Falls more inspiring and less crowded, with three sets of falls crashing very close to the trails, and you'll get wet from the mist and all the water crashing throughout the canyon. Bring your camera!
The Chittendon Road pullout, farther north of Tower Falls, takes you to the trailhead for Mount Washburn, a good hike, and near the headwaters of Antelope Creek. There are usually a collection of people with spotting scopes there and a little farther east along the NE Entrance Rd, and frequently enough, you'll spot a grizzly or wolves on the opposite (south) side of the valley, and if you look hard, you'll see several sets of elk-antler and mulie-antler sheds harsh white against the green slopes of the valley-but you've gotta have good optics.
As far as the Old Faithful area, you've got to have the girls see "Old Faithful" geyser, and then the lobby of the Old Faithful Inn-incredible architecture.
Also, north of Tower Falls, Roosevelt Lodge has lots of fairly-primitive cabins for rent, but again, need to check availability. There are also showers that you can use. The restaurant at Roosevelt serves a good steak, and/or bison prime rib, and the bar has cold beer, even a few micro-brews, as does the bar at Old Faithful.
Slough Creek up in the NE corner is really beautiful, and has good camping and fishing. There, and anywhere in YNP as the sun gets lower, have good bug spray, either DEET or a really good botanical bug repellant. Don't forget to take HUNDREDS of pics...you will be glad you did, even when after a few days something seems "mundane", take a few pics extra. As you look back on the trip(s), you'll be surprised at how some mundane pics give you the best memories