DS and I do Descartes Cove together. He is fascinated by it and will work on it with me for an hour at a time. I'm teaching him math the way DH teaches the kids to cook. He sees me do math, I talk about the problem solving process, explain definitions and I let him do little jobs like add up numbers (chop celery?) and anything else that he already knows how to do.

That way he is exposed to lots of interesting concepts and higher level reasoning. He loves it so I figure it can't hurt smile