First step, breathe. Relax. You'll be fine. Your sorority wouldn't be the oldest if your sisterhood wasn't strong.
1) Do a "3 positives, 1 negative" evaluation of your chapter. Do it in a casual setting (not chapter meeting). Do you have great academics? Won Greek Week? Have a great philanthropy? Great chapter diversity? Emphasize that in recruitment.
2) The "no contacts" thing isn't true. You've got an alumnae base to use. You're the oldest chapter, remember?
3) Bring your alumnae around during your pre-recruitment warm up. They've often got great ideas from the old days and may be able to help you out.
4) Try to do a non-recruitment event for the campus. We did a movie night in one of the lecture rooms. Got a Greek movie, some popcorn, put up flyers, and people from other greek organizations and PNMs came. After the movie we discussed how it was different from the reality of greek life. It was good, casual, and not overbearing.
(Another idea is to hook up with another org (sorority or fraternity) and bring a speaker to campus. A couple organizations on my campus regularly hook up with our NPHC groups to bring diversity speakers to campus. )
5) Letters, we've got letters, we've got bags and bags of letters... To that extent, wear your letters often. Make sure people see your sisters answering questions in class in letters, around campus in letters, everywhere in letters. Identify yourselves with your letters.