For your 10 y.o. son, I would recommend an IZH 61.

http://www.pyramydair.com/s/m/IZH_61_multi_shot_air_rifle/76

It's perfect for a young shooter, and his size. And, you don't have to spend big bucks either.
I had one for a while and it's perfect for a small kid. Also very accurate with good power out to 40-50 yards. It gave all of my tuned HW springers and rammed guns a run for their money it was that accurate. NO JOKE, this is a very good and under rated gun.

S.W.A.G. it