I think I am going to have give this game (all these games) a shot with my kids as they grow up. I can imagine myself as a kid really enjoying this kind of thing.
Take a deck of card, remove all the face cards and then have an addition war. Each person is dealt half the deck (now 40 cards). Keeping the stack face down, you begin by each turning over the top two cards. The highest sum wins. What a great way to learn addition!
There are some great variants of this game at the site,