870's arent that expensive. i would just buy the youth model 20 ga. its only120 bucks at walmart where i live. andif he find out that he doesnt like it then you have an extra gun for your self..
just my two penny's

if thats to expensive i have a youth model 870 used i am wanting to get rid of.the barrel isnt rifled butmy wife used it this year and shot 4 deer all 50yards or better.. couple ofoptions for ya
good luck Jeff Smith.