3) DO NOT take a gift TO a wedding. (Even envelopes.)
Perhaps not an American etiquette rule but it is traditionally done in my area of Canada and among our polish friends (mostly envelopes in this regard)
If you are not Spanish, DO NOT have a money dance. And never, never, never start a money dance for yourself (ie asking a DJ to start it, or including it in your wedding schedule) no matter what your culture is!
Some other European cultures do it as well.
Actually I found it to be a scheduled in quite a few itineraries for the MC, which is designed by the B&G, so technically they don't start it, the MC does, but its hair splitting.