Generally, FT has been laying out the lines with a thin row (10') for people to setup a single row of EZ-ups on front of the line, with an aisle, between that and the camping area. Effectively, the front row is too thin to park a trailer. Taking a look at the FFOH'18 layouts will give you a picture of how FT typically lays out the lines:
Event:
https://static1.squarespace.com/static/5845acd8e6f2e1f15e5c3c55/t/5b3a85c5575d1fe4d577fcaa/1530561989903/ff18_map_OUTLINED-01+(1).png
Camping:
https://static1.squarespace.com/sta...0780dc5c/1496775724181/Camping+Info+FFE17.pdf (pdf)
FFS last year and pretty much all FFOHs have been laid out in a variant of this. FFW was not, but that property couldn't be setup in this way. In past, people with trailers who didn't purchase a camping spot could park them in the day parking area and leave them there overnight (assuming the day-parking area wasn't a mudhole . . . that was fun
). It was a bit of a hike, but not much more than the late camping arrivals.
That being said . . . the Double flightline (FINALLY!!! I've been lobbying for this at FFOH for YEARS!) with the event sandwiched in between may change some things a bit, but I expect it will be some variation of this pattern
So . . . for your friends, I'd offer two strategies -- either buy a tent camping spot to park their trailer (tent vs. RV is more about the site size than the hardness of the walls, and most airplane trailers will fit into a tent site), or plan on hiking in from the day-parking area. Where will that be at AP? No idea. They haven't released an event map yet.
In any case, I recommend these watchwords for TOTAL ENJOYMENT of FliteFest:
Semper Gumby -- Forever Flexible.
Expect it to be cool, but don't expect it to be like you expect