The more crowded the park is likely to be, the more significant the
AAA FastPass option is. With AAA, you also get free parking, but you aren't that likely to use that staying on-site. I believe that everything else you get through AAA you would get if you booked through Disney Travel (I don't have my list in front of me, but I think you get: Pin and lanyard, priority seating to one of the shows, $10 ESPN card, EE, Toontown madness; there's even more if you purchase with a Disney Visa)
BUT... I would think that it would be difficult to change or re-book through AAA for if you are planning on going on or around 7/17. It wouldn't hurt to ask your AAA agent, but I wouldn't count on being able to do it. Even if you could, depending upon how you booked your trip, there may be cancellation or change fees associated with it. I think you should just be thrilled that you have reservations to at the DLH at this particular time.