single-card multiplayer recommendations

I'm taking a long car trip with my nephews (7 and 9 yrs old) and wanted some recommendations for good DS games to play together from one card - each of us has a DS. We have Mario Kart for racing goodness.

Any ideas? Co-op play would be cool but I think that's pretty rare in DS games. Lego StarWars II has it but that game got scary bad reviews.

thanks for the link
sorry for clogging up the boards