Federal campgrounds can get uppity about "workshops" using their facilities -- requiring permits, etc. As long as they know it is a non-profit, freeforall sort of thing no problem.
I was assisting for a workshop that traveled up the Oregon coast -- one of my jobs was to get campsites each night. No problem with the state parks, but got in trouble at a US Forest Service campground at Sutton Beach. I got visited by two ranger types who started to talk about the need for permits, etc. Fortunately I was also working as a seasonal Forest Service wilderness ranger at the time, and they granted me some "professional courtesy" and said just to take the "workshop" sign off the bullentin board. I put up a sign saying "Weston and Adams Family Reunion" instead.