My daughter's getting Dora Saves the Snow Princess for Wii, Daddy is getting Call of Duty: World at War and the family is getting Guitar Hero III...
My 4-year old daughter loves Carnival, Wii Sports and Wii Play. Since the only other two games we have right now are Link's Challenge and Monster Truck Racing, those are the only ones she can "play" (and I do use that term loosely on some of the different aspects).
There are A LOT of games out there for Wii that are geared towards young children, one of the best parts of the Wii system in my opinion. Go take a look at your neighborhood Walmart, Sam's, K-Mart, Best Buy, Circuit City or Game Stop (G.S. is VERY expensive though). Take a look at Amazon.com as well. There are all kinds of fun stuff for the kiddos.