We had a combination of AP's and hopper tickets over the last year during 3 separate trips, and only the ADULT AP holders needed to have their fingers scanned(correctly called a "biometric reader"). As a matter of fact, my DH and daughter had the same character on their hoppers, and I held onto everyone's for safe-keeping, so I am sure they got them mixed up a time or 2. We did have one hopper that did not scan twice during our trip, and the CM at the gate waved us through and pointed us in the direction of guest services in the park to replace the hopper.