Attendance Tracker - support for guests

In attendance tracker, we'd like the ability to track guest arrivals with members. For our club, members are allowed to bring guests, but there is an associated guest fee, so we'd like to include a count of # of adult guests and # of children guests associated with the member family attending the club. A simple numeric drop-down for the adult/children guest would work for us but the ability to add custom fields to the process would be really ideal.