My sister and brother-in-law are both semi-religious theists, so I'm a bit reluctant to introduce him to anything as hardcore-atheist as Less Wrong, at least right now. Going through that huge theist-to-atheist identity transition can be really traumatic. I think it would be better if he was a bit older before he had confront those ideas.
I was 16 before I really allowed myself to accept that I didn't believe in God, and that was still a major crisis for me. If he starts getting into hardcore rationality material this early, I'm afraid it could force a choice between rationality and wishful thinking that he may not be ready to make.
If he is gifted and interested in science, introducing him to lesswrong, rationality and the Singularity could have a substantial positive impact on his academic development. What would be the worst that could happen?
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