dgf,
Recoil's a bit higher than in a full-weight rifle - physics & no free lunch.
Really depends on your nephew's size & sensitivity to recoil. The Wife's 5' even & 100 lbs - no problem with the 7-08 & we really should have picked up another .308 for her - a bit better selection for bullets in the heavier weights.
If you reload, options for down-loading a bit are in the sky's the limit area - or maybe use a bit lighter bullet.
With the 18.5" bbl, I went with Barnes XBT for the alleged added penetration. With 165s @2400fps, they've shot right through three elk so far - one end-to-end. Other than the mentioned MPBR being a bit closer in, I'm not at any disadvantage in the least by not having the higher velocities.
Get that boy a M7. If for elk-sized critters, I'd go for the .308 & if for deer, the 7-08 or .243
BTW, we're getting right at 2600fps with 120s & ~2500fps with 140s in the 7-08