I have had used guitars shipped directly to my home from Guitar Center for free, and on one occasion I returned the guitar to my local store because I did not like the tone, and they refunded 100% of my money, including shipping. So I think you can return for ANY reason at all, so no need to unpack the guitar in the store if you would rather have the convenience of doing it at home. You should probably check to make sure this policy has not changed, though.
As for the guitars that you selected, I have heard good things about Yamaha Pacificas, and Yamaha has a great reputation of producing high quality in lower priced instruments, so I would probably go for one of those.
Good luck, and I hope you will enjoy many years of playing with your son.
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