My Younger Nephew is kind of obsessed with video games, and doesn't have access to a video game console at home, so we've hatched plans to have him come over and play at my house. The catch is, at 5 years old, I don't think he really has the reading skills (or possibly even the interest in sustained narrative) to get really into the story-based RPGs that make up the bulk of my gaming. (Also, games like Dragon Age 2 seem a touch...traumatic for a 5 year old.) I have a few games that I think he might like - Katamari Damacy and Lego Batman spring to mind - but I'd like to pick up one or two more just to have a variety of things on hand.
So I'm looking for recommendations for good games for kids. They don't necessarily have to be games specifically developed for kids - first person shooters or driving games would probably be right up Younger Nephew's alley - but I'd like to avoid exposing him to excessively adult content. (I should probably hide Grand Theft Auto before he comes over.) Bonus points if they've got a co-op or multiplayer mode that a kid and an adult could play together.