How about a "General Store" game? Pick a variety of "goods," assign each a cost and sale price, ranging from $1-$12, then put together simple "orders" and have him figure out the bill, as well as cost to the store and profit. After he figures out three or four bills, have him add the profit from those sales together to see how much the store made that day. You don't need a time limit on any of it, and the transition from addition and subtraction to multiplication is fluid. It's the "Lemonade Stand" method if you think about it.
Concrete association in something like register math is very powerful, and layering levels of success and motivation using the concept of gain makes the child feel useful, like they're learning how to use one of Dad's tools so they can help him instead of drilling on seemingly abstract number tables.
If he's into games, you could try the one so many people my age learned a ton from, The Oregon Trail. There are modern versions of it, even on iphone/ipad etc. I'll tell you, even the most easily distracted kids quickly learned what two wagon axles and 20 lbs. of grain cost verrrry quickly!
That's just my two cents, I was ADD/gifted/dysgraphic and that was what made the most sense to me back then.
