Good luck AmandaMarie! Your outfits sound just lovely, I'm certain you are going to look great. As for them being too formal, well I honestly think that ZTA is pulling out all the stops for this colonization so I get the feeling that you can use the dress standards of formal recruitment as your guide.
Remember that you can look on the Zeta website
http://www.zetataualpha.org if you'd like to know more about their organization in advance. It might spark some conversation topics for your interview and for philanthropy night.
You can also look on the NPC website:
www.npcwomen.org to learn about all the sororities.
Best of luck, can't wait to hear how the events go!
violets