i think that is awesome you are putting together a retreat.  my best advice would be to make it creative and fun.  something that all the girls would enjoy doing.  i loved what we did for my new member retreat and i wish all other retreats were like it.  we went to a cabin kind of out in the woods.  we had a fire going outside and made smores.  we all slept in the same room in the cabin, the cabin was actually a place that girl scouts stay for their camp outs.  that has been the best retreat i have done since i joined delta zeta.  i hope this helps in anyway.  good luck with it! 
