Just an FYI, balloons are a cool idea and I have actually used them before, but they are not an "approved" target material. Targets technically need to be paper or the like so the "scraps" and "remnants" are biodegradable.

I know this first hand as we were "educated" of this by a ranger out at Pawnee. Just a heads up. Its to bad because its a cool idea and its a "reactive" target, I used to fill them with baby powder also so you could really see them when they pop!