I should note that the Turbotax license allows you to install the program on up to 5 programs that you own, but you are not allowed to transfer it to someone else. You could prepare your son's return on your computer, but you are technically not allowed to give a copy to your son to install on his computer. I don't know if customer service will overlook that or not.
Also, in the past, Turbotax was not licensed for overseas use. I checked the current license and I did not see a specific ban on overseas use, so I can't tell if it is a general program restriction or a restriction on the Amazon US copy.
I can suggest that your son can try to prepare his return online using Turbotax Deluxe Online, and then instead of paying the fee and filing, he can download the data file and send it to you for final e-filing. That may work.
