I don't think you'll have anything to worry about. I reserved through Disney first to ensure we got the resort and dates we wanted because I couldn't get through to AAA online while travelling. Once I did though, I got the exact same package for my family's trip for $222 less. DW was happy because this pays for Character breakfasts and other fun things!
I was really happy with AAA and Disney reservations. They were both great and when I cancelled the first Disney made reservation the cast member was really wonderful about it, thanking me for coming to WDW regardless of how it was booked.
If you are using MidAtlantic AAA, I recommend calling and asking for Rosann at (888-203-6348 ext 4) as she was wonderful in helping me get the vacation planned and even made suggestions to help because we are bringing a two year old with us...
Good luck and enjoy!