As far as lodging... we actually call the whole upstairs part of the dining hall the Guest House. The smaller side (Guest House West--what you referred to as the annex) has one bathroom and three bedrooms, beds as follows:2 singles, 2 singles, and 3 singles, so regular capacity is 7.
The larger side (G.H. East) has 2 bathrooms ... and 6 bedrooms, beds as follows:
1 double, 1 double, 2 single, 2 single, 2 single, 3 single, so regular capacity is 13.
That's a total of 20 bed spaces. We've had more fit in there using air mattresses, couches (there are 3 couches in there), sleeping bags, etc. Of course people can camp. And we have some other housing space--a couple apartments that can accommodate 2 people each (again, unless people supplement beds with couches, air mattresses, etc.). How much of this will your group want? (You can discuss this with Ellie when she calls.)