Shot my first deer (a long time ago) with a husqvarna (FN) 30-06. Somebody was watching over me that morning! I have shot a few more with a 30-06 but mostly migrated over to various 270s, with 25-06, 280, 7mm mag, 300 win mags liberally sprinkled throughout. My son shot his first one with another 30-06 husqvarna (fn) downloaded a bit to keep recoil reasonable.
Starting from scratch I would lean towards a versatile caliber for bigger stuff (assuming there was a reasonable opportunity for that in the future) and download initially to reduce recoil. Something like a 270/7-08 etc in a gun they can physically handle well.
I am unconvinced that young hunters should start shooting at big game too young, they are mostly not mentally and emotionally ready for that. Nothing wrong with them accompanying a parent/uncle/grandpa for a few years first to enjoy the experience, understand that there is a lot more to it than just shooting something and see if it is for them.
