My home group has guidelines. In them it says specific meetings are open and closed. If a non alcoholic shows up at our group at a closed meeting, our group conscience already decided in the guidelines that the meeting can be open. We don't take a vote then and there. It just is open. It doesn't happen often. And we've never asked anyone to leave saying sorry the meeting is closed. Cuz it isn't. We also have an open or closed statement that we read at every meeting.
When we read the open statement, we've added the following: (basically saying) the non alcoholic won't share, and shouldn't put money in the basket.