A few weeks ago we got a Kinect for our Xbox 360. The Kinect sensor allows you to use your body as a controller for games. The implementation that Microsoft makes it very easy to get into the games.
We used to have a Wii, and the kids, especially the younger ones, had a hard time using the Wiimote, especially when absolute movement is needed. The kids really enjoy the Kinect. They haven't had any problem playing the games. They really like playing Kinect Adventures and Kintectimals. Our 6-year-old daughter has a lot of fun playing Dance Central.
I would recommend Kinect for any family with kids, especially if you already have an Xbox in the house.