Alice and I talked about this before and said we'd figure it out on a case-by-case basis.
We have used the gallery for bag making on a couple of occasions. Both times people still came in to view the art and it was pretty cool and interactive. I don't think that's possible with a room of people doing dance...
It is very difficult to keep people out of the gallery when things are busy - especially at night. I really feel that if the gallery does not want people hanging out in there and drinking at night then we need to put some doors up and close the gallery at 7-8pm.