Use of Meeting Rooms Outside Library Hours

We are revising our Meeting Room Policy. Currently we have a group of seniors who meet at our library for [really healthy] exercise in the morning before the library is open. They have been doing this for about [many] years. As we know the participants very well and they want to meet before the library is open, we have allowed them to come into the building when it is not officially open.

There is no staff on duty. They open and lock up when finished. This has been a wonderful service we can provide our seniors in a rural community where there are very few options for group gatherings. We would like to keep this practice in place.

However, as we discuss the meeting room policy, we realize that we would not be comfortable with having other groups be in the library when we were not open to the public with staff present.

Can we write our policy to allow this group to continue with the current practice, yet limit other groups to only use the meeting room when the library is open.