As an avid hunter and reloader, allow me to present another consideration:
OP, what kind of hunting will he be doing? 2-300 yard shots across bean fields and the like? I'd look at one of the previously mentioned calibers. Small, fast bullet where drop is minimal over longer distances. Possibly in a compact version for reasons mentioned later.
***OR***
If his local hunting conditions are like mine (hunting in woods, hills, etc) where the longest shot is maybe 150 yards, then while all of the high velocity rounds mentioned above can certainly do the job, you are not limited to them.
I grew up hunting (as a left hander) with a bolt action 270. It wasn't until I was about 30 that I wanted to try something different. I traded that .270 for a left-handed 30-06 and loved it. Still, however, I realized that I was hunting with a 300 yard gun and a 3-9x scope and 95% of my shots were on deer at 40-100 yards. I was hunting with 3x the rifle that I really needed. On top of that, I was hunting out of box blinds and walking through woods and the long barrel on my rifle was always kind of unwieldy to poke through the window on the box, or was snagging on branches in the thick stuff, or whatever. So I wanted to try something else again.
If your son is left-handed, or you just want a more ambidextrous option, or you don't want a bunch of your meat bloodshot from the cavitation caused by high velocity rifle rounds, and you hunt in closer quarters (up to 150 yds or so), then consider a lever action rifle like a 30-30. Recoil is less than most if not all of the aforementioned calibers and the 30-30 has been killing em dead for over 100 years. With a slower moving heavier bullet, less meat is bloodshot and you can "eat right up to the hole". Lever actions are easier to maneuver with in the woods and in a stand than standard bolt action rifles with 22-24" barrels, although if you are set on a bolt action rifle, you may appreciate the youth or compact versions for maneuverability even for a grownup.
You could consider a Marlin 336 in 30-30 or even a Marlin 1894 in 44 magnum. Many hunt with a 357 magnum rifle but I wouldn't try taking a deer with one beyond 60-75 yards. There is something cool about hunting with a lever action rifle. I intend to do a lot of my hunting this year with my Marlin 336 Texan (30-30 with 18.5" barrel and straight stock) and cast bullets.
At some point, popping a deer at 40-75 yards with a 270, a 308, or -God forbid, a 7mm Magnum- begins to feel like using a hammer instead of a flyswatter.