I'd recommend Carnival Games, Kinectimals, Fantastic Pets, or Disneyland Adventures as a good kids' Kinect game.
In Carnival Games, you play classic games that you would find at a fair or arcade. You can win prizes and wear costumes.
In Kinectimals, you do mini-games to train a pet tiger (or other big cat of your choice). They've also recently added bears to the mix.
In Fantastic Pets, you do mini-games with and care for magical creatures (unicorns, dragons, etc.).
In Disneyland Adventures, you run around completing quests for the various Disney characters in a full-scale replica of the California park. You can also do games in the rides.
Hope this helps.