The Golden Ticket
At the start of the new semester, or in whatever frequency the school decides, the machines are refilled and a golden ticket is hidden inside one of the books by the author selected by the school to come for an author visit. The school choses this author they would like to have visit, either in person if the author is local or virtually, and a date is determined for the event.
Upon discovery of the golden ticket, the student presents it to the teacher/administrator, to scan the QR code on the ticket to reveal a special message from the author.
The finder gets the honor of keeping the special golden ticket but the entire school "wins" the meet-the-author event, and at the event, all of the students in receive a free copy of the book prior to the event. If the book is not appropriate for older or younger readers, they can take part in the event but will get a book at the next event, for a book more suited to the other grades.