A.,
My youngest who is now 8 weaned herself when she was about 1 year old and will not drink any milk at all. It is so bad that if you try and make her she starts vomitting. We have tried Soy, Rice, flavored cows milk, nothing. Her Dr says as long as she is getting calcium through other things it is not a problem, she does eat chesse, yogurt, nuts etc as well as her multi viatmin that has extra calcuim. (she doens't eat milk based ice cream either), but has not problems with milk, because she can eat foods that have dairy in them, she just doesn't like the taste or texture of liquid milk. I would have a talk with your sons doctor and they can give you a list of other foods to make sure he gets the vitamins and diary fat that he needs. But a child does not need to drink milk to be heathly.
Good luck
Amanda