We had a Heaven and Hell party and used packing peanuts to fill a floor and make it look like you were standing on clouds. terrible idea. Even though it wasn't the party floor people still had wet shoes or brought drinks to that floor and the peanuts got a little wet. wet packing peanuts are a NIGHTMARE, they stuck to the linoleum floor for awhile, and to this day there are still some stuck to the carpeted stairs that we cannot get off.
We were very lucky to run into a brothers friend who's dad happened to have a TON of packing peanuts because he had some book business or hobby or something where he had a lot of things shipped to him. we also got a bag from a local store that had things shipped to it. check local stores and run around for awhile because yes, packing peanuts are expensive for the volume you need. and you will need more than you think, the peanuts quickly become pushed aside or crushed and flattened as people walk though it.
good luck!