If you call WDW directly, you can get the AAA discount as a room only reservation which allows you to make changes or cancel for a full refund up to 5 days prior to arrival. When the better discounts are announced, you can call back and easliy change to the better rate with no hassles. I have done this several times. I just got a postcard and was able to change my AAA rate to the postcard rate with no problem at all. For a room only reservation, I think dealing directly with WDW is the easiest way to go.