I had bad hand-eye coordination for the longest time, and also have always had trouble just sitting still. I think crocheting helped me with my hand-eye cordination. Since I started, at age 12, I have noticed a major difference in it. Both knitting and crocheting is a good activity for me b/c I can move, but do something useful with it, if that makes any sense at all.
Congrats on getting your son to knit! That is totally awesome.