Wear a fancy souvenier t-shirt that has "Las Vegas" in glittery letters, maybe with
dice or cards below the words.
Fishnet stockings with a skirt that's a wee bit too short.
Youngsters like to wear flip flops, try that.
Or switch to a pantsuit as mentioned. The most daring visitor (not a baptized dub)
could wear blue jeans.
You already mentioned heavy make-up. What about a total Goth look?
Sunglasses indoors is always a great idea. Maybe not so dark that they could
think it's a deliberate thing.
I went to the Memorial in clean sneakers and no tie. If I were daring, I would have
worn a "dress" hawaiian shirt, but I chickened out. That would work great for a
sister- a hawaiian shirt with a short skirt and flip flops. The fishnets would not
work with that outfit, so don't wear any hose.