This could be a huge money maker for a club if it turns out AMA would allow it at a club funtion.
A HUGE money maker, HUGE! Until of course the plane gets knocked down on the first hit. How much you charging per shot by the way? $50? You guys should leave these kinds of huge money maker idears left alone for guys who wear camouflage clothes for a living. If you want to go play paintball, then go play paintball. If you want to shoot at object then go shoot off some clay pigeons, you know something designed to travel away from a crowd of people.
Think ... what happens when you shoot the planes wing or elevator off and it flies into the crowd? You ever been hit with a paintball round? Do you think it's possible? Same goes with airsoft gun, you are trying to disable the functions of that airplane. Does this still sound like a great money maker idear to you? Do you really think for a second the AMA is going to cover this, this wasn't a joke?
Let's also hope you have a good pilot on the sticks and doesn't steer the plane towards the pits or crowd, that could turn out to be interesting. A guy with a gun and a guy with an RC plane ... what a hoot.
As far as the AMA goes read rule number 3 of the code, that's the don't do dumb stuff rule. Of course the AMA is not a rulemaker only a decision suggester. While you most likely won't see a dime if you hurt someone, you could also lose your club charter. I think something like you saying is more well suited for a field, somewhere out in the sticks, not an AMA chartered club. Remember, AMA members are all in the same boat and if you do something dumb, it effects all the members.