That's a great question -
here are some random thoughts -
1) are you and he prepared for the experience of having to work to "get" new concepts? It can be tough on a family that isn't used to it. You may want to practice on some non-adademic challenge.
2) Aleks.com - buy a month's subscription and run through it, just to see where the "needs more practice" places are.
3) Touchtyping (bet ya' knew I'd say that!)
4) Will he have missed the school music program?
Best Wishes - I'm so happy for you!
Trinity