From my experience, Kids are much more persistant than adults. Persistance =/= patience, though. I think a game for kids should be quick to get into, or at least start off with a bang, like how FF7 starts off with a rather neat dugeon, giving you only a short intro as to who you are and why you're doing it, culminating in a rather gimmicky boss fight and a Super Metroid-like Speed-Backtrack-so-you-don't-blow-up kinda thing. Whereas Final Fantasy 6 spent, like, a half-hour at least before you could actually do anything.
Or like how my first real RPG was the original Final Fantasy that I found on a website. It literally dropped you into the game with barely any info whatsoever, and I knew jack squat as to how to play. Hell, I didn't even know the basics of equipment management, and the NES version didn't tell you much in the shops, IIRC. It was all supposed to be in a manual I didn't have. But I learned. After 3 hours of dying against freakin' Goblins, I learned. I experiemented, I explored, I extrapolated, and I eventually started talking to the townsfolk, which turned out to be much more helpful than I expected...but eventually I beat the first boss and felt like a freakin' champion. I've seen this quite a bit with kids. So long as it isn't boring, they'll keep at things, just because. It's like how some kids could beat Mega Man back in the day. They weren't gonna let the game beat them. If there's a problem, more than likely they'll find some way to solve it, even if it involves searching or asking for a little help.