Let him have fun and let him guide it. My 13 year old pitched one inning when he was 9. He hit the first two batters in the head and didn't want to pitch again the rest of the year and we let it go.
At 10, he started working on it. He worked on it but didn't want to pitch in games. Again I didn't push him and then toward the end of the season we played a tournament and we were in need of a pitcher. He said he would do it. He struck out the side and pitched 2 more innings with no runs. He became confident and excited about it.
At 11 he pitched more, started enjoying it but still prefered other positions.
Last year he became our #2 pitcher on Sundays for his 12u team. He came up to me this off season and said that he wants to be a pitcher. I said he has been doing a good job, he said no dad. I want to be a pitcher and would like to commit to lessons.
He has been doing lessons for 4 weeks now and loves it. The moral of the story, let your son dictate what he wants to do.