Dress shopping is SO much fun, a thought, because it is most likely to quite hot and very AC'd get a short dress, if it works for you, something that is layered or with a jacket or shrug that you can put on or take off. You most likely will be hot, I know it sounds goofy but the temp is a hard thing to work with inside the hotels. Have fun, Vegas is nice, tell everyone you are having your wedding or on your honeymoon, you will get lots of freebies.
It's fun. Best of luck and lots of love.