Coolers-
But they were not complaining about how loud the toilets were,
or the parked car noise,
or the concession stand noise level....

They were complaining about just having those things silently exist in view from their property.
Electric or not, those folks want to limit what others have on their property, not just the noise.
Perhaps the club should sue the neighbors for ruining the clubs view of the 'pastoral refuge' they built houses on.

I think the quick fix would be for the RC Club to get into the Hog Farming business, and run a high density feed lot on that property . That will make the neighbors want to get a nice smelling RC Field back on the site in no time.