Just an FYI that if some people do decide to stay at Fort Wilderness for SSS 2019, there is an option when you book the site for a "Campsite Request".
See screenshot below...
I think the wording is poor but to me it appears that you can request a campsite that is near someone else's campsite under the "Request a Nearby Campsite" section.
All you need is the person's first initial, last name and their check-in date.
I guess we'd need to know this info from the person who will be checking in first.
I did actual booked the Sept 5th to the 9th, but am thinking about expanding the dates, as in move up the check-in date