I would suggest those in actual attendance to drown out the “gay-pseudo-marriage” ceremony on the float with duck calls.
I know a company that sells them.
http://duckcommander.com/store/duck-calls
That’s a great idea. But if anyone is going to the parade, maybe they could pick up a couple hundred cheap noise makers at a party supply store or through oriental trading. This way more people could be involved in the razzing.