One thing the .30/30 in a traditional lever action carbine has going for it, is ease of carrying and quickness of getting into action. Over the course of a long day, a 12 year old would have an easier time carrying a Winchester 94 at the balance than he would any bolt gun, simply due to the thin profile of the lever gun. If you're hunting in the Belair Forest, assuming they haven't cut it all down, the .30/30 would be a fine choice, but the .243 has the edge if your hunting where there has been some cutting, or if you prefer to hunt the surrounding open country. If you handload, a .30/30 loaded with 125 gr Sierra bullets to about 2600 fps will be surprisingly mild and flat shooting, and will anchor a deer without much fuss. If you intend to buy ammo off the shelf, and the kid wants a scoped rifle, the .243 with 100 gr bullets is probably the right answer. Good luck.