That's a good question, and I think it depends a lot on your kids. In the theater we were in, there were some really little ones, like 3s and 4s. They seemed to enjoy it, but I heard a lot of questions for the grown ups after the movie was over. There's enough funny stuff that they'll probably enjoy it no matter what, but there is a suggestion of death in the form of self-sacrifice. (I don't want to spoil it for you, and that's as cryptic as I can get without spoiling.)

Hope that helps! I can get more spoilery/specific if you like.