I am also looking for my 9 year old for Christmas, and ran a thread on several different forums on this topic about a month ago. Several bows come highly reccommended, and if price was not an issue I would go with the Browning Micro (either Midas or Adrenaline). Very adjustable both in DL and poundage, and can be adjusted up to my states minimum of 40 lbs for hunting. The Pse is also mentioned frequently, as are several others. If he is big enough and your pockets deep enough, the Bowtech Miranda is probably top of the heap.

All that being said, I very well may buy a used PSE Spyder from my parents neighbor. My boy wants to bowhunt but I think another couple of years will make all the difference. He got a doe last year, and his first buck on Saturday. Had that buck in about 10 yards and nearly put him into meltdown. I think he needs some more experience before he starts slinging arrows at live critters. So if I get him a bow that won't pull 40, well the the law is the law, right? It will buy me another year or two of maturity anyways. Plus I don't want him trying to pull too much weight just so he can hunt. He is self motivated to say the least!!! Just because you can buy the bow doesn't give you the right to shoot at game, you have to be proficient with it, and he still needs to learn that. Anyways, my .02