See if he'll take a paintbrush, marker, or pencil and see if he'll follow your lead in doing a "how to draw" project. You get your own pad of paper and he gets his own pad of paper and you follow the steps togeather. I think that covers a lot of early lessons because you're learning to follow directions, there are sequential steps in order, and it works out those fine motor pre-writing skills. It's also very forgiving if you're not exact your picture can still look very good, while early attempts at writing usually don't look great to the kid. I had good luck with having him draw with a pencil and then have him make it darker with a marker because that smooths out wobbly lines a little bit.
Also google "the big numbers song" on youtube if he can't count to 100 yet, or schoolhouse rock "count by 5s" if he can. And after that use bedtime math .com for a daily math word problem like "If you have two cookies and eat one how many are left." If he doesn't get the problem of the day reword it with a smaller number or replace the objects with cookies or candy.
