Damn, you're just full of excuses as to why something can't be done, aren't you. When the national square dance convention rolls into town, they have to have sound equipment for all of the halls, meaning up to 100(or more) speakers, amplifiers for every hall(plus spares), speaker stands, all the cords, stages, musical and sound equipment as needed for the Ghostriders Square Dance Band, booth dividers for the vendors area, etc. Gee does this sound familiar? All of that is supplied by people from the hosting state or rented from local sources. Things that are used at all the conventions are taken by the members of the next convention after the present one they helped with is over. This eliminates shipping charges and makes the items available prior to the next convention for any needed repairs and planning purposes.
As far as volunteers, it takes HUNDREDS to handle a convention that hosts THOUSANDS. To get around the training problem you mentioned, the dancers found a simple solution. As volunteers are assigned to their committees, they are requested to help out at one or two conventions prior to the one they will be running. After their first convention, they are expected to help train those that will be running later conventions.
This summer's convention, in Marietta Georgia, already has 3050 registered dancers. They are coming from all points of the US and abroad, so far accounting for 49 states, Australia, Austria, Canada, China, Germany, Japan, Netherlands and the Philippine Islands, with almost six months left before the convention starts. Gee, are your events starting to sound small? As for RV's, the convention staff had reserved an entire campground with 344 spaces. That makes it sad to see you panicking over maybe 20. As far as hotels, they have sold out six of nine in the area, leaving only 238 rooms still available.
After typing all of the solutions the dancers have come up with, it seems to me that a bunch of "old hill billy dancers" have made the AMA's excuses look foolish.

As far as finding an area that can handle a national flying event, Redmond Washington's Marymoor Park can handle the requirements you listed for a flying field. The park has a flying area and, all told, the park covers almost 700 acres. There is plenty of parking though some is a bit of a walk. There are campgrounds in the area as well though, IIRC, dry camping on site is discouraged in the park.
Another site that is ideal for gliders is Fort Casey, on Whidbey Island. One of the local gliding clubs flies there quite often as the winds that come down the Straight of Juan De Fuca and lift are ideal. Since they normally fly over Admiralty Inlet, instead of land, there isn't any one in the flying area and, when it comes time to land, there is a large grass field that can be used located nearby, behind the gun casements. There is a campground on site, plenty of parking, army barracks that can be rented out for lodging, all within walking distance to the windward side of the park. Have I destroyed your arguments yet? I've found working and proven solutions to all your issue that eliminate them and turn them into excuses. Once again, your excuses don't hold water