Poopers (also sometimes called "Snaps") just make noise. It's made by the contents of the paper "popper" striking each other and making a small explosion when you throw them. They are completely safe. I use to pop them between my fingers. They won't hurt you.
Champagne Bottles is basicly just confitti under preasure. You pull a sting and it fires out the front. Harmless, unless you like point it right at your eye before pulling the string.
Those things are no where near as dangerous as the Fireworks that are sold at stands. In fact I don't even think they are classifed as Fireworks, which is why places like K-Mart, Target, and Wal-Mart can sell them. You won't find things like bottlerockets, Firecrackers, Sparklers or rockets at those places. Just go by and look at them next time you are there. I bet they are exactly what I told you they are.