The .280 is a fine choice for your son. I would go with something more commercially available, but if he has confidence in the round he is more apt to spend time shooting it and more time practicing. These things will make him a better hunter.

The .280 is basically the 30-06's thinner brother. It is a little smaller in the bullet area, but performs nearly identically under hunting conditions. If that is what he wants it is certainly a great cartridge.