Our son sailed with us throughout his whole life... 18 days old the first time. I'm happy to say that he's a boat owner himself now and sails/races on OPBs as well.
We designed and built a littly opti-like dinghy when he was 4 or 5 and he started sailing it on his own not long after. He learned to row in it too, and it provided hours of entertainmnet (and independance) as he was growing up on the water.
My son is 3 and we are about to buy our first boat. I want so much for him to enjoy and love the whole experience. I'd like to know more about that little opt-like dinghy you built. Got any pics? Or a web site with a tutorial???