Well, the ages range - 8 (Joey) 14 (Alex) and then my nephew who's 20. Ya - super gore is not really an option for any of them, even the 20 yr old for certain reasons.
if they like sports games, the ESPN NFL game is a good deal.
Viewtiful Joe has gotten good reviews. cartoonish karate game. i played a demo version and i dont recall explicit violence.
browse the newstand for gaming magazines. they offer good reviews and ratings for all types of games.