Dont forget RITZ, who has 130 acre private airsoft field with lots of great players out your back door.
I would let you get some practice running a game with our crew. It would be good practice for you before doing a very large game.
We are in the planning stages of another huge invite summer game right now. Its alot of work and takes a team to pull it off. Its the same weekend as border wars was. There is alot to plan for from the pig roasts to the scenario details. Your idea is good and sounds fun to play.