Let those people leave early. Create an event people can feel like they can sink their teeth into for an entire evening. People who get tired easily, or don t have a tolerance for hours of listening can just leave early. Additionally, however, CC managers can assure a more interesting venue by offering incentives and many ways to be involved. Spice up the action with audience participation activities and incentives.
Tiles face up in a pool, allow each person attending to play ONE word.
If you bring one, you get to take one. Bring two, take two. It might be best to limit this to three from each person. Some people might especially look forward to the coffeehouse because of the swap. Your local UU Poets Co-op members could run this if you have representation in your congregation, or the coffeehouse management, or the church in general.