I think the lighter bullets will work just fine for him. Shot placement is the key to any bullets performance on game. You may want to check and see if Remington has any reduced loads for the 06 that will work to build his confidence during his learning curve. If all else fails he can kill an elk with that .243 with a good bullet. It's not the optimum situation but it has been done before. Maybe a good friend may have a 7mm/08 or .308 that would be willing to lend you, but there really isn't too much difference in the recoil. Browning makes the REACTOR recoil pads that fit in a pocket in a shirt for trap shooting and that may be the ticket for you in this situation or you could always add a brake to the gun with a thread cap for later usage. You have time and options at this point and will find a workable solution.