I went a similar route with a .243 for a smaller kiddo. A factory Winchester Ranger with short LOP, and a Leupold Freedom 3-9x40. I actually wanted some weight on the rifle to reduce recoil.
I called Hodgdon and Nosler. Using H4895 I followed their starting load for reduced recoil/downloaded loads recommendations for a 100 grain partition, IIRC. The employees I spoke to regarding the effecacy of that load both stated that was the route they had taken with their own kiddos.
The load printed 2" @ 100 yds all day long. It would shoot better groups on occasion but I knew it was plenty accurate for our use.
The furthest shot taken was 75 yards, most 50 or closer, on our feet with a tripod, still hunting on whitetail does. One shot kills every one. Small sample size of a few, but it was quite effective and a lot of fun.
A 140 gr. Nosler Partition, starting load with the reduced load H4895 and learning to get close, with accurate shot placement, will be filled tags all day long.