If you sign up with AAA, then you are not able to add another discount to that special rate. You can only hold 1 discount on a reservation, be it a room discount or a package discount (like the free dining offer). Disney seems to pretty much offer a discount for different times of the year, except the major holiday weeks/weekends (pres. day, easter, july 4th, thanksgiving, christmas, etc).
You can go ahead and book your package at full price (aka "rack rate") and next year as discounts get announced you can call and have one applied to your ressie. If something else comes out for your same travel dates, you can call and have a CM compare the offers, and pick the better deal. Some travel agents will do this for you (keep an eye out for discounts) if you book through them, but also know if you use a TA then you cannot call disney directly and make changes to your reservation, you will have to have your agent call and do that for you.
