Is DisneyParks.com part of the Disney.go.com site (the official Disney website) or is it a third party website?
If it's part of the official Disney website, you can make your reservation and if a better offer comes up you can modify your reservation. If it's
free dining and you already have a package you can modify it to include FD if you meet all the required criteria (available on your dates, right room & resort category, rooms are available, etc.) If you have a room only reservation, you'll have to book a package and cancel the room only.
You will have to initiate any changes to your reservation. Disney isn't going to contact you if new offers/specials are announced.
If you book through
AAA and any new offers come up you will have to contact AAA since they own your reservation and any changes need to be done through them.
If DisneyParks.com is a third party website or a
travel agency, I wouldn't know what their policies are.