I put my two cents from trying to recruit people back in the day in JDE's topic, so I will give them here as well. That is awesome that you had the connections to get something that big, but if this is your first one they might be scared there will not be a big enough turnout along with the m rating. It is a good idea to run your own at your own host to build the scene, then you can show these bigger organizers that the scene is serious and they would be missing out on quite a bit of money on their end to turn you down in the future.
If they are worried about certain age groups with an M rated game, just try to set up a event later in the evening that is 18+ or something if they are going to be that strict about it. I hope I am not excluding any one of your twelve players that are coming to your house, I am just offering suggestions to appeal to the organizer in the future. Until then, build that community that is coming and show them you are serious about the community you are hosting.
