As an ex-MEVP, I remember chapter retreats all too well....
The fall retreat that I planned was informal...not required, so we went to a local park and started off the day with Tootsie-Roll Pops, where depending on the flavor you pulled (Cherry, Blueberry, etc.), you had to say the same number of things you enjoy about being a sister of ADPi as there were letters in your flavor (so if you pulled Cherry, you would say 6 things you loved....Chocolate and Blueberry were always a lot of fun!) We also tie-dyed shirts that we brought from our "home" (dorm, apartment, etc) and then played on the playground at the park.
The spring retreat we held at a local church in their youth room (one of our sisters was a member of the church). We got together and actually did a sisterhood building activity led by our TCC before she left for another chapter, the usual standards presentation, we watched movies that night and slept overnight in the room, and then in the morning we revealed prides by doing a memory-type game.
Other retreats I went to were pretty similar when it was the spring retreat....preparing for elections or officer transition, meeting in prides, brainstorming ideas for Songfest, etc. The fall retreat was also a time to get things together for our informal recruitment (door decs, prides, etc).