You can get the AAA discount IF IT IS AVAIABLE [for room only reservation]for your time through Disney directly or AAA. You can only book a AAA PACKAGE which gives you the reduced room rate but reg cost on the rest of the package with AAA you only get the AAA perks, such as Diamond parking pass booking a package through AAA.
If you book a AAA package and a code comes out that is lower for which you otherwise will qualify you can call AAA and have them call Disney and apply the code. I just did exactly that,. My AAA package was about $200 less then straight Disney, then when the code came out the switched from AAA discount to code discount and saved ANOTHER $400.