The ages of kids are on the room reservation, however when you make a dining reservation you do not have to necessarily attach each person on the room reservation to that dining reservation. If you are three adults and one child, sometimes the system books it as 4 adults, sometimes 2 adults, 2 kids.. When checking into the restaurant, they will ask how many adults and how many kids. For example, last year we went to Ohana, my husband checked in and they asked how many. He said two adults, two kids, not realizing that our 11 year old son at the time was considered an adult. They printed up the ticket and gave it to the waiter. There was no questioning of age or checking of room reservation. But you are correct, you can't purchase a dining plan for a child, if they're booked as an adult on the room reservation.