Awl, Julie you'll do fine! Just try to not overthink TOO much, and just be you! Maybe pretend you've done this a hundred times before, and just dress instinctively, whatever seems to come to mind. Sometimes I'll pretend I HAVE done something, like I'm already used to it, then try to creatively "remember" how I did it. Try to put the event into a "been there, done that" context rather than worry and do something special for a first impression.
Besides, with that personality of yours, they're gonna be so focused on loving and laughing with you, I'm sure the clothing will soon be forgotten after that initial moment.
Unless we're talking fishnets, miniskirt and tube top... 😉