Yes, Swan/Dolphin typically offers AARP discounts, but only if they are available for your travel dates.
The best thing to do is to either price your trip out directly on the Swan/Dolphin site (you will see a box to click to check for AARP discounts) or call the hotels directly (sometimes the hotel reservation staff knows more about special offers at the resort than the general reservation line.)
Here is the Swan/Dolphin website:
http://www.swandolphin.com
When you price out the trip, you will see total costs with resort fees, etc. I would then price out the Beach Club to see if you are getting a better price. In my experience, Swan/Dolphin has always beat out the WDW EP resorts even with the fees.
As PP noted, you can use your old MB's, but you will only be able to access your park tickets on them. Swan/Dolphin doesn't participate in the MB program.