Assign each kid a playing card:
Ted - 2 of spades
John - 5 of hearts
Dick - Jack of Diamonds
Keep the list somewhere. Kids have X numbers of chances to use their pass.
Gets punched just like you mentioned. Once the card is "full" (they have used
up all the chances) the card is collected and they are done. Kids who have
punches left at the end of the term can use them for credit on an assignment
or something (Depends on the teacher)
I do like the sticker idea. You could add a date & destination slot to the
front or back of the playing card.