everything goes in my space bags. i had no problem with my formal dresses...but they are material that can be easily folded and once brought out the wrinkles come right out. if in doubt, you could always take a small bottle of wrinkle releaser with you (buy the wrinkle releaser and then a small spray bottle so you don't have to pack the big one).
and i would ask the room steward for the vacuum
that is the spacebag website