I am in agreement with A-Abe here. You could chose a lot of different calibers but a 280 or 270 would excellent places to start. Not knowing the age, ability and size of your son..... a 30-06 could be too much recoil for him although it could be tamed with a brake and a high quality recoil pad. I agree that the 30-06 is arguably the best caliber choice around but I have also seen grown men put their rifles down after one box of shells and chose to be spectators.
Abe and I go seperate directions on Browning weapons....I like them.
My two cents worth.
Keep Your Powder Dry,
Dave.