D3RPG Core Rules

While there are plenty of RPGs for kids 5 and over, D3RPG is one of the few systems that teaches you, the adult, to tell collaborative stories with your pre-kindergarden age kids, as young as 3 or 4 years old. 

D3RPG not only gives you a simple role-playing system that your 3 year old can enjoy, it includes both both scaffolding and advanced options, so that you can  modify the game to make it friendlier for younger kids, or more complex for older kids looking for a more complex challenge.