[Alumiyum]

When I was active we COBed three times and did things like:
-Ice cream sundae bar on the hall, movies and manicures, walking to the locally owned coffee shop and playing games on the porch, going to our university's soccer game and bringing hot chocolate, game night, etc.

We have a hall in a dorm as well as a chapter room, but just about every campus has a lodge or student center where rooms can be rented for free or very little. They might also have helpful equipment available, like a projector and screen if you want to have a movie night. Whatever you do, have your girls practice small talk before the events and remind them to be personable...the things you do in preparation for formal recruitment. It's even more important to be friendly during COB since you have a smaller number of girls in attendance so they aren't being passed off constantly. Remind sisters to talk to the PNMs more than each other. Telling sisterhood stories, funny anecdotes, etc. is a good way to show the PNMs what your chapter is like.

Plan ahead so that everyone can attend and look into the facilities your campus has available...good luck!