The Staff are your hosts and you look to your host/hostess to set the mood, and take your cue from them. NYE is about lively partying. And, the Staff should encourage the crowd to party
If it were a wedding, or a Mother's Day/Easter.....it would be totally different.
I went to a friend's wedding where a Staff member crossed the line, crossed a boundary (this wasn't at Disney), so it does happen....but NYE is not the same as a wedding reception or brunch.