What about a homeschool PE class for him, or aikido or horseback riding or some other physical outlet?
Mine weren't as young as yours when we started homeschooling, but we included PE as part of the deal. My son played rec league soccer four times a week, my daughter's goal was to learn to ride her bike (she has some physical issues that made this a yearlong goal)and we went to park playgroups with other homeschoolers at least twice a week. Plus field trips to locations that usually involved hiking or being outdoors. I found we had to keep up a pretty high activity level if I expected them to sleep at night.
The other thing is that I think, when homeschooling (especially if you lean toward unschooling) it's imperative to let them know what's open for discussion and what isn't. Mostly we ran our "school" pretty democratically. But there were some times when I had to play the dictator card, and they just had to learn to accept that. The other option was to go back to a regular public school situation-- and no harm no foul if that's what worked out, but those were their choices.
