Good luck on your project Dood. I know how it is having to deal with a bunch old fart plankers that don't fly helicopters at all. You mentioned you were the only CD, which would mean if they have other AMA sponsored events wouldn't you be the one doing it.
Why they would even begin to question your desire to have a heli event I am not sure. (but on the other hand I guess I am sure)
Also I am not sure if this has been mentioned and perhaps you already know it since you said you are a CD, but if you sanctioned the event for a Saturday and Sunday, that means the event is in effect for both those days or 3 days if it includes Friday.
This means if there are still a few heli guys around late Sunday evening that have paid an entry fee to fly in the event, the event in effect is still going on and they should have prior. Otherwise just list the event as a Friday and Saturday event.
I have had that problem of plankers coming in after lunch Sunday wanting to to fly because they saw that most of the heli pilots had gone. Even if you raise a couple thousand dollars for the club they don't care. They just wanted what they want at the time and that is to fly there planks. So for as many days the event is listed, that is how many days the event is suppose to be held. If all the heli guys have gone by 2 PM then there should be no problem for the plankers to fly. Hope it works for you dude!
By the way, I sent you a second PM message a couple of days ago, you never responded to it so maybe you were busy.