AAA discounts vary from 10 - 20% off depending on the season and resort type. You mentioned May - which is regular season and would give you a 10% off the rack rate of a deluxe. More info on the AAA rates can be found
here.
The main reason I booked through AAA was to be able to add on the dining plan to the MYW package (and still keep the AAA room discount). I have heard from one person on the DISboards that their DU
travel agent was able to book the AAA discounted rate + tickets + dining.
There might be better discount codes coming, but they are not guaranteed especially if room occupancy is high. Some people randomly receive e-mail or postcard discount codes, but not everyone does so you can't rely on that. I've also read that some have been able to add on the dining to their postcard or e-mail discount codes + tickets.
Hope this helps... we saved $268 by booking with AAA travel and were able to get the dining plan in addition to our AAA room discount plus tickets (for value season).