I answered this in your other post so I will be brief here. The SKS will kill deer with the proper ammo, but I would opt for the 30-30 myself just for the ammo selection.
SKS's are a bit heavy as well, with really nasty triggers, but if he gets to shoot it first you will see if it works for him.
What is a .30-.30 in very good shape worth? Without a scope
Depends on the gun and who made it. More than an SKS most likely though.
Paul