They started allowing AP holders to book the Dining plan this year. I'm sure someone will chime in on the particulars. I don't know if you can add it to a room that isn't booked at an AP holder rate but I wouldn't think that should matter since you would be paying more for the room if you don't get a discounted one. You may have to go through the passholder website or call the passholder phone line to get it added to your room only package.