I use to work at AAA in the travel department as a
travel agent and they do have great rates. You also will get the promotions that are on also. So if Disney is having a sale you should get a cheaper price with AAA then with Disney directly. The only thing that they sometimes do at AAA is that they only have a certain amount of rooms at the aaa rate especially with free dinning and such so make sure to go ahead and book but keep a look out for specials. You should be able to call and have your package even though it is under deposit changed to the special rate. And if I am not mistaken there is also a place to put the little savings code so if you do happen to have one make sure to give it to the TA to see if they would be able to get you an even better rate.
Also there are other AAA only perks.. I work for AAA Carolinas so I know that we had the free VIP parking, a special Storytime with Belle as well as other things like luggage tags and a VIP discount card to get discounts on food and such in the parks. So make sure to ask about that as well