Take him to a pro shop and have the pro there fit him and test him out different stuff... Check and be 100% sure of all laws regarding age and draw requirements... A bowhunter education course wouldn't hurt either....

I personally started bow hunting when I was 10. Started shooting long before that, but couldnt pull the required weight so I had to wait. Here in Texas you can hunt as young as you want but only with an adult untill you're 12. For two years my mom would sit in a bow blind a hundred or so yds off (but with direct line of sight), so I could hunt. None of the bow stands on the property were condusive to two hunters....