My chapter had the same problem this year. So myself and a few other recent alum came dressed for the themes, just to make it look like more people. We tried not to talk to rushees too much, but we did if it was necessary. Our panhel allows it (as well as sisters from other chapters) as long as it is clearly marked on the name tag. Just one note of caution, one sorority had another chapter come in for 12 rounds and all the rushees loved the girls, but then 8 rounds came and the other chapter wasn't there, so it didn't fool the rushees one bit and many of the rushees cut them after that. Try not to focus on having few numbers, focus on the fact that you are "rebuilding" and looking for a great nm class to help lead the house. In my experience it is all about a positive attitude! Good luck!