Children's tickets only based on height? No, not by age?

When we bought the tickets, we checked IDs and took a photo of our child.
Children can take a look at the ID card.
Child ticket, show your ID card, and take a photo.
When we bought the ticket, we checked our ID and took a picture of the child.
Children can take a look at the ID card by themselves.
Child ticket, check ID card, and take a photo.