1/ "Survivor" might not be the best idea for a theme. I have never watched the show, but as I understand it, the weakest contestant gets voted off periodically... as a rushee I would not like to feel like I might be "voted off" as "weak". Just have your rush parties, and offer bids to whomever you like... rather than have all your PNM's constantly worried that they might not make the cut.
2/ For "unique" just let you and your sisters speak for themselves. Don't strictly pair sisters and PNM's - each PNM has to meet the majority of the chapter before she'll feel comfortable joining.
Good luck!