Here are my recommendations: Diamond Infinite Edge Mission Riot or Craze Hoyt Ignite maybe Ruckus These are all very adjustable bows with exception of the Ruckus. The Infinite Edge is probably the most cost effective bow but, it's fast and quiet. These bows would allow for more than enough adjustment for him to use for as long as he may want. I think this is important for a growing child and his fathers pocket book.
I live in NH your best bet is to go to a bow shop like Brian's Archery they'll take care of you. You live in Mass so it's not that far and their the best bow shop in New England.
I would have to agree, the Diamond Razor Edge would be a good choice. They are very user friendly when it comes to changing the draw length. No bow press required. I also believe with this bow you can start with a youth bow and do the limb exchange program that Diamond offers.