i'll combine those two answers with a little more info...maybe ofcourse maybe it'll make it more confusing I hope not.
If you have a room only reservation...no matter who it is with you can not add dining to it.
Dining has to be 'added' to a package (room + tickets) and room only can not become a package. Dining is not a stand alone item. Tickets are required, and required in the form of a package, not purchased separately - from disney or elsewhere. However you can get 1 day base tickets for your party to meet this requirement, they do not need to be length of stay. Everyone booked in the room must have the same tickets and dining options.
To get a package booked from a room only, you must cancel the room only and rebook, all original deposits refunded; you must make new deposits. This will become a new reservation. Since you will be booking a new reservation, it wont matter if you are cancelling the original from disney, aaa, or whoever else. BUT packages with a aaa discounted room can only be booked at aaa. Your discount remains the exact same amount as it was for the room only, your tickets and dining are not discounted. I suggest getting atleast a hold on a aaa package before cancelling your room only.