Don't know if it'll help or not, but when DS was showing an interest, DH made up a game. He'd hold up X number of fingers and say "let's add X more". Then, with a flourish and great sound effects, he'd add the fingers and DS would count them. As it progressed, DS would come up with the factors and tell Dad to do the game. He did the same with subtraction and called it the "Take Away Game". DS seemed to really like it. Of course, this only works up to 10, grin.