my little guy has been enthralled with the DS since he was 4
he loved games that I thought would be too hard for him
stuff like advance wars, etc
but he didn't care about winning, he just liked the music, and the fighting
he was happy to just create stuff and blow it up, over and over again
I think that's more the thing
don't worry about whether or not they're playing it "the right way" just let them have fun with it