This topic can cover pages and pages and not repeat a word. First, I'd like to direct you to a few websites. Put "Salmon University" in Google and you'll see a wealth of information. In depth information on reels is on Alan Tani's reel repair forum. Finally, look up ifish, piscatorial pursuits and gamefishin.com.
I prefer reels smaller than many salmon fisherman but you can make up your own mind. As long as I get between 150 and 200 yards of 20 - 25 lb test line for a trolling reel, I'm happy. The classic Penn 209 is fine for moderate cost. I'd step up a few dollars and go for the Penn 310 which you can find online for about 75-80. The Daiwa Sealine 17 is a favorite of mine. The Shimano Tekota is a fine reel running something under $200 as is the Penn Fathom (I like the 15 size in these).
Spinning reels should be matched to the rod. Many of us use the 2500 size on 8 1/2 to 10 1/2' rods rated 6-10 lb test line for the rivers.
Good luck on your trip!
