I wouldn't hesitate to use a 30-30 for deer. As long as your son knows his rifle and how to place the shot properly, it should do just fine at 100yds. As a matter of fact, I wouldn't be surprised to discover that it's easier to find ammo for it these days, either.
I'd be more concerned about the length of the stock than anything. Just make sure it's not so long that it prevents him from being able to properly set the rifle into his shoulder and cheek. If it's fitted right, he can probably shoot a pretty large caliber rifle for at least a few boxes of ammo which should be good enough to get him acclimated to the rifle before he goes out hunting with the boys!
Have fun and post pics of his first deer!
--Wag--
I'd be more concerned about the length of the stock than anything. Just make sure it's not so long that it prevents him from being able to properly set the rifle into his shoulder and cheek. If it's fitted right, he can probably shoot a pretty large caliber rifle for at least a few boxes of ammo which should be good enough to get him acclimated to the rifle before he goes out hunting with the boys!
Have fun and post pics of his first deer!
--Wag--