The rule is not one ADULT in a room for the room to be considered that status for things that go by room--it is one person of any age.
There are benefits that are "per person" like lanyards, merchandise discounts, etc. These will be given to the appropriate person, noted on the appropriate KTTW card, etc. There are other benefits that are "per cabin" like on line registration, signing up for excursions, invitation to the CC reception, etc. These are awarded to the room based on the highest CC level of any person in the room.