You can contact Disney directly, That is what I have done for my upcoming reservation this December. You do not have to go directly through AAA. I have seen other posts where you can save 10% on your reservation, but I think I read either somewhere on AAA or another site where AAA members can receive 10% - 20% depending on time of year and such. I only received 10% on our upcoming trip.
If you want a room only reservation, all the above posts are correct. However, if you are interested in a package with the AAA discount on the room portion of the package, then you need to go to a AAA travel agent. You can't book a package through disney with the AAA discount.