
Quoting
jumanji
Why do you feel he is too young to know that your husband is not the Daddy who made him? That he has a heritage with a richness and language and culture all its own? My neighbors have two adopted (from ages younger than your son's) children from cultures visibly different from their own, and both have known from Day One across the street that each has a Mommy and Daddy who made them, and a Mommy and Daddy who are raising them.
I'm sorry - you are only making things more difficult for your son, IMO. And you may find that it backfires on you when he discovers the truth. Really - (in my opinion) you should be doing everything possible to help him learn where he comes from via his Father. Where You chose him to come from. Something to think about...