The FAA won't be involved as you're not commercial and under the umbrella of "hobby" model aviation.
If you're looking at dropping Nerf darts (or similar "soft" projectiles) you're biggest concern will be that of safety - and that you're planning to fly over people and/or structures - which would be a violation of the AMA safety code.
Is anyone really going to care? Probably not. It's even less likely anyone will come after you for doing it over private property with "willing combatants" - just don't put self-documented unsafe acts on YouTube for the rest of the world to say "see!, they're ALL evil and out to get us, shoot them ALL down!"
You can have a lot of fun dropping "bombs" onto a fixed target, or to friends who try to catch a Nerf Dart, parachute or other soft item after taking a couple steps away from the pilot, but myself, I'd shy away from using it in a game of warfare - there's too much going on to pay attention to the safe operation of the model, and too much that could go wrong in the heat of battle.
A lot of people don't understand their liability when operating model aircraft. Even if your "willing combatants" accept the risk of being under a flying aircraft - what happens (who pays the bill) should something happen and someone get hurt by the plane?