... what lock box should they get for their only handgun? ... I was thinking about one with a finger combination lock to it. Because when kids grow up they are in to everything and would eventually find the key and I don't believe I would recommend one with anything to do with electronics but I'm not sure.
What have y'all found that works or don't work
First, I think it's important to confirm that we are talking only about a minimal level of security. All of the small gun "safes" or lock boxes that cost +/-$50 are only intended to do what you are talking about: Keep kids from playing with the gun. There's nothing wrong with that goal. Some folks will bash certain devices because they "aren't strong enough." So, yes, unless you're worried about Junior taking the safe/box out into the driveway and slamming it down on the cement repeatedly until it pops open, just about any safe/box is "good enough."
Second, Get one that meets your needs, given your goals and space limitations. Does the dad think it's important to have quick access to the firearm? If not, again, it really doesn't matter what you get. Go to Amazon or MidwayUSA and find one with good reviews that's in your price range that is set up like you want. As you know, some boxes open like a car door, where the door just swings toward you on hinges. Others lift up like a trap door in the floor (I think these are called "drawer safes.") I originally had a small safe with a traditional swinging door on my night stand, but soon found that I couldn't set anything in front of it if I wanted the door to open. For my available space, it wasn't a great choice. I now have a drawer safe there. Of course, the limitation with that style is that you can't set anything on the top of it, because it all has to be moved to open the door. But, that is less of a hassle for me, so that's what I use.
Third, as for the type of access mechanism, I agree that a key shouldn't be the access method. Knowing that I am not terribly smooth in an emergency, I don't want to have to locate a key and open a key when time/speed might be a factor. My box is electronic (accessed with a number code) with a key backup. My combination is extremely simple and uses only two buttons. I can easily punch in the code in the dark if need be. I avoided the rotating number dials due to not being able to unlock in the dark. If you're worried about a little one finding the key, lock it in the family safe where they keep their important papers. Or, put it in a place that inquisitive minds won't be looking (taped to the underside of a dresser drawer, inside the back of a picture frame, etc.) I test my safe about every 3 months and it gets a new battery every hunting season when I put fresh batteries in my flashlight in my pack, so I have never ever needed the key.
Lastly, make sure that it's big enough for the gun in question along with whatever else is going inside it (extra magazines, etc.) I've got a few of these types of safes, either at home or at work, and they tend to get small rather quickly!
Good luck!