Yes. A good AAA travel agent should be able to apply general public discounts and personal PINs to a Disney reservation, just as any travel agent can.But can you not book with AAA and get the promo codes. A good TA will get you the best discount. An AAA TA should be able to book for any promo including their own if that happens to be best. And if you book with them you would get their perks.
I've never done this I'm just asking.
We use AAA at US for food and merchandise.