I believe you were able to figure this out; but in case others are interested, here is the solution:
Track the adults as "clubbers". (Just broaden the definition of "clubber" and think "participant" or "student".)
Under Admin > Club Setup > Club Names, Logos, Dues & Points: create a new "Adult Class" club name by clicking the "New Club" button in the toolbar. Use the radio button selection to "Copy point values and dates from existing club" and select one of the existing VBS clubs.
When you enter a new "participant" you will need to manually assign the person to the VBS Adult Class (club) since the automatic assignment will only work for gender/grade combinations through grade 12.