I would opt for either a 270 or a 7mm-08. If you are concerned about recoil look at the reduced recoil loads now offered by Remington and others. Once the shooter is proficient AND needs the option for longer shots, step them up to normal, full-power loads. If they will be shooting under 200 yards for deer and smaller game, just keep with the reduced recoil loads and you're done. Also, make sure you have a really good recoil pad on the rifle from the start and try to avoid a youth model as they are generally lighter and will kick harder. Plenty of eye releif for the scope too, don't want them to get bit. And don't make them shoot paper to start, put a plastic gallon milk jug out at 35 yards full of water (food dye red or green or blue for fun) and let them shoot those for a while. Make it fun and keep their minds off the recoil. Only shoot a few shells and then switch over to a .22 semi-auto and just have fun with it.

Good luck!