NWP '19 here. Nothing is required to be done before he shows up. With that being said, NWP is at about a mile high so he can uses this time to pretend to prepare for I-day physically. The Durbecks will ease everyone into it, but the PT sessions will be easier, and more enjoyable, if he can already handle it ahead of time.
Your MOC should already be aware of the FFS and for many, that is enough validation to receive a nomination. Of course he still needs to finish the application, but it should be a little simpler since he will have USAFA as his #1. It is also important to note that with a FFS, your DS does not need to win the slate, he just needs a nomination. He should definitely bring it up respectfully in his interview as a confirmation that the committee knows he has it.
Congrats to your son! He will love NWP!