An easy to learn universal roleplaying system for children!
From the introduction:
Stargazing is a roleplaying game for children, it is about imagination and creating. The Core rule is that anything can be done as long as it's plausible in the game setting. The game mechanics are simple, using 2D6 (2 six sided dice), anytime the players try something that sounds like it should be rolled on, set a "Target number" or "reachable" modifier and have them roll.