Saxophone player and small flashmob to dance to "Single Ladies" by Beyonce

I want to propose to my girlfriend in a public and cheesy way - basically wanted a sax player to start playing the main hook from "Single Ladies" by Beyonce ("If you like it then you should have put a ring on it") and then a small group of people (10-15 maybe?) to start dancing in unison. Once my girlfriend works out what is happening I will pop the question (and hope she doesn't embarrass me back!!) Date is 29th/30th of this month, so not a lot of time to arrange - I hope someone can help out!!!