Boom Blox for sure, I played this over Thanksgiving and it is fantastic, and at one time we had a 30 year old playing against an 11 year old and both were having a blast. It's like Jenga/bowling on steroids. Learning curve of about 5 minutes too, which is about all an 11 or 9 year old would want to put up with.
de Blob is also supposed to be great (I've not played it) but you download it from the Nintendo store.