I would get pokepark for Wii, after playing it myself, I can assure you its appropriate for a 5 year old. It would probably seriously bore any kid over 5 years old though. But if you need a super easy game, this is the way to go.
I wouldn't get any movie games, those games are A LOT more difficult than they seem, I have also played these types of games, and they are hard for an adult to beat, I can't imagine a 5 year old beating them.