Was a scout master for 15 years, and never got to go to Philmont....even though I live in the same state. You folks are lucky it will be worth it.
On the other hand the LaPlata Mountains are 40 minutes away, where we spent most of our hiking/camping time. Very easy to get your 50 miler trek there and most times you never see another human. Lots of deer, elk, and bears, but not many humans.
One bit of advice to drill into your son's head.....do not keep food, candy, or even
in your tent or anywhere near it....or it will get visited by something in the middle of the night. Skunks, racoons, and even bears. Nothing is worse than waking up at 3 a.m. to screams. For me the experience was with a scout waking to a nudging at his pillow, flipped on his flash light and found he was staring nose to nose with a skunk.....could have been worse! Instill in your son the importance to listen to and being obedient to the rules of the trek. I have lots of stories of what happens to scouts who don't think that's important.
Don't worry about the reloading. It's an introduction to whet interest, no more. The best training for that is at your local gun club programs.