Difficult as it is, try not to be apprehensive, or at least don't show it. I'm sure there will be butterflies, but it's important that your wife get a glimpse of who you will be once all the ups and downs smooth out. You want her to see someone that is sure of herself and relaxed and confident. That will give her a sense of being able to trust you and who you are.
I made a big move like this over Thanksgiving. We (wife and I) hosted a dinner with one of my sons (34) and some close friends that I had previously come out to. I had just privately met with the wife and matter of factly announced who I was, the husband and I have a lot in common and have talked extensively about this, but no one had seen me really all femme. I was wearing heeled booties, embroidered skinnies, a lovely tunic, bra looking plenty boobie, eyes made up and lipstick, hoops in my ears, hair in an up do. No question I was all girl, but very classy, I think, and nothing over the top. I was a good hostess and spent my time addressing the needs of my guests and cooking dinner. Engaging in conversation like I had done a dozen times before when we had gotten together for dinner and drinks. I was just normal me, but wearing different clothes. It went off beautifully and when we parted it was hugs and smiles all around and I realized I hadn't been the least bit uncomfortable and so neither were they, in fact, I really hadn't thought about my appearance at all.
I don't know if that gives you any clues , but just let your own wonderful self come through and I'm sure you'll have a good evening. Hugs, Toni