I would be very hesitant to hunt with something at that weight. Like the others said, try to get his weight up a little at a time and maybe he'll be up to 40 by season starts....

As for range, I'd keep itto 15 maybe20 yds in the field with that draw weight, and use the heaviest arrows you can find that will shoot from the bow(to help in Penetration).

Acombination of cumulativecircumstances results in an effective hunting range of roughly 60-75% of your range in a controlled environment. Have your son run back and forth to your practice target say 10 times(or as many as it takes to get his heart rate up and his breathing heavy), then pick up his bow and shoot without resting. Just a trick my dad did with me. Have him practice from hunting situations. Out of a treestand, One shot drills etc.

The more you push and challenge him in practice the better chance for success he'll have. Congrats on having a son who's already caught the bug for it, and Best of Luck to him!