Oh I loved being a Rho Chi. It was such a great experience.
Make sure you have a comfortable backpack to carry all this stuff in. And don't forget to carry a few things for yourself too - definitely bring a water bottle and some small snacks. (you'll end up sharing both.) Also sunscreen. If events go late into the evening, bring an extra layer to keep you warm.
For the PNMs, definitely bring tissues (not just for crying, but for allergies, sweating, etc.)
Also, advil or tylenol, bobbi pins, hair ties and a small mirror/compact. Breath mints are good, but those little listerine strips that dissolve in your mouth are fabulous.