I am assuming that you want this feature for the 'early' pick-ups? It wouldn't be necessary for the normal end of club p/u's ..right?
But do this to put a custom check box in your Check-In grid:
Admins > Club Setup > Custom Fields > under the Display Name column, type Parent P/U or Early P/U, or your own title) then click the check mark at bottom left to save.
Go to Check-In tab, open 'viewable column' tool, (click the (*) at far left of secondary band) and tick the created P/U box to activate. Now the Parent P/U box is available for all clubbers.
[Note: in the Windows app, the custom fields are handled under Admin > Club Setup > Club Names, Logos, Dues and Points using the button on the toolbar. akj]