I run a 3.5 campaign with my two adult sons (ages 25 and 23), my friend and former co-worker, his wife, and their oldest son (age 11). Their younger son (age 4) also "plays" with us, in that he has his own initiative card (with a photo of his head grafted onto a picture of a halfling paladin), his own figurine (usually a green army man with a flamethower), and his own pile of his dice. When it's his turn, he tells us what he wants to do (generally burn things with his flamethrower, or throw a grenade at the monster), we let him roll a couple dice and tell us what numbers he got, and then I pretend to document the damage on my sheet. Sometimes I even throw in an extra monster just for him to deal with - "You enter a room filled with an orc shaman, a half dozen orc fighters, and a midget tyrannosaurus rex; Joey, you'd better take care of that dinosaur for us, okay?" 
I've been playing AD&D/3.0/3.5 with my two sons since they were 10 and 8, and they were amazed at the "upgrade" from the HeroQuest board game that we had been playing for a year beforehand. HeroQuest got them accustomed to the basic fantasy tropes, and to the concept of teamwork to achieve a common goal, but it was still a board game with limited options as to what you could do on your turn. They both thought it was very cool that in AD&D, when it was their turn they could (try to) do virtually anything at all.
Johnathan
I've been playing AD&D/3.0/3.5 with my two sons since they were 10 and 8, and they were amazed at the "upgrade" from the HeroQuest board game that we had been playing for a year beforehand. HeroQuest got them accustomed to the basic fantasy tropes, and to the concept of teamwork to achieve a common goal, but it was still a board game with limited options as to what you could do on your turn. They both thought it was very cool that in AD&D, when it was their turn they could (try to) do virtually anything at all.
Johnathan
