Definitely check with your campus Panhellenic. The chapter that I'm currently advising had sisters from another chapter come up last fall to add numbers (and show the fun of being a national--doesn't matter what chapter you are from, you are all sisters and are there to help each other out). The visiting sisters really only did the singing, etc. They didn't actually rush any of the PNMs--and if the PNMs approached them with questions the visiting sisters directed them to a 'local' sister for the answer (tactfully of course!) The visiting sisters were also only there for phase two (philanthropy day). I think my girls really enjoyed it as well because they got to meet more sisters than those just on their campus and also learned some formal rushing tips.
I would definitely say go for it.
Fraternally,
Sarah