Definitely not black flats - that dress is much too glam!
I would wear black opaque tights and high black heels. The wedges might work, it depends on the wedges if they are delicate enough, but black heels always win (even if they are sandals or more edgy that's fine). As for colour showing through, wear a nude slip to prevent this.
You can keep the top half super pretty - pretty cuff on your arm and fabulous big earrings. Think Chanel or Valentino. Keep the coverup pretty and fitted, like a little blazer (black or white or any colour really). If you dont have one, buy a really cheap one for $20. Blazers are one of the few items of clothing that look great even at the lower price range because they are always so sharp and expensive looking.
Alternatively, if it's an indoor event, nude hose could be great.