I also would say to stay around the 70 gr mark - if it shoots well. Inside of 100 yds, that should be ample engergy to get the job done.

70gr and the new 240gr PT Gold might be worth a try too. They are tipped but expand well. I would guess if that load shoots well, it would be fine out to 100 yards or a bit more.

My friends favorite youth load for his 14 year old is 80gr and a 250gr GoldDot. Accuracy and expansion were excellent at 50 yards in his ML.