The good money was always about keeping it small and making it sound huge, not in volume but the soundscape...You gotta sound like the record as they have no interest in the band whatsoever, they just wanna hear a good sound that they know.
Back in the day a 'four piece' with a top notch keys player with one hand on strings and the other on a Fender Rhodes/piano and everyone singing backing vox, which was an absolute must, could make it work...but you had to be good and the keys player usually got a bit extra.
I did it for a while in the 80's but setting up hrs beforehand and hanging around for hrs will wear you down. Anyway good luck with the endeavour....Playing in a smart environment doing good music against a packed floor full of people dressed up and having a good time is a cool way to play music....Last and final time I did it was a recent dep at a big do at a Hilton Hotel...Low ceiling, heaving ball room, twas a very good nite indeed.