“I would probably personally not object to optional mixed seating during the meal except for the fact that the dancing is in the same room and all of the men sitting around the women’s dance floor have front row seats, which I do not think is appropriate.”
It doesn’t have to be set up symmetrically. I have been to weddings that had the (mixed) reception tables on the men’s side of the mechitza for dancing, so there was no reason for men to be on the women’s side.