Have a closing activity or ritual that will bring a sense of closure to the group.
Consider having this closing include a chance for participants to share something about what they have gotten from the retreat.
Encourage participants to complete the evaluation form before they leave.
See if someone will write an article about the retreat for your district's newsletter (Sunshine), for your W&R newsletter (Womanspirit), or for UUWF's newsletter (The Communicator).
Remember that you are responsible for checking out with the site manager(s). Make sure they are paid. Make sure you leave the place as you found it. (It's a nice touch to invite the site manager(s) and kitchen crew into your final gathering for a round of thanks.)
Give yourself a pat on the back. Give your co-facilitator, and everyone else in reach, a hug. You have just completed a big job and, hopefully, had a good time while your were at it.