I've added a group called PAN Liverpool and I've put all members who attend or have attended a home game in this group. When creating a new event on the calendar you can now set it so that it is only visible to members of the PAN Liverpool group, this will ensure that only members who have been approved can confirm attendance on the event.
Any new members who join can only be added to this group by request. Either they, or an existing member, must ask me to add them to the group.
