You cannot really hold a genius back. The simply don't play like other kids. Even when you send them outside to play a little, they will be looking at things and doing things differently. They will NOT fit in socially AT ALL with their "peers." Let him study. He is happy.
Their peers aren't the other play ground kids. They'll find FreeRepublic some day and find a whole bunch of genius+ peers.
Reminds me of the movie Parenthood. The little girl is a genius, and is completely freaked out from something as simple as the old "sliding thumb" trick.
Sure you can. Happens every day. Ask anybody who has joined Mensa, even the ones who have experienced great success.