JMO, but, it seems to me that if you've got a kid shooting, he's going to be a lot more likely to flinch and gut shoot a deer with a .30-06 than he will with a .243.
Are you saying you "have" to jump from a .243 all the way to an 30-06?? What happened to the 260 Rem.? 7-08, 257 Roberts and several others???
All of them are a better choise than a .243 and won't kick the sh** out of a smaller person..
DM