Hello Amy!
Boy, are your parents in for a surprise! Honestly, I don't think you can go wrong with either resort and with the economy we are currently in, I would vote to stay within your budget and go with Port Orleans Riverside (POR). I have stayed at POR in the past and it's an absolutely lovely, tranquil resort. I also noticed you have a question pending regarding Downtown Disney (DTD). In case you didn't know, POR offers a very relaxing boat ride to DTD which your parents may enjoy.
That being said, if you are able to find a special for the Beach Club (BC) area, you may want to consider upgrading to the deluxe resort. I say BC area as I think you should also look into the BC's sister resort - the Yacht Club. I think your parents may find this resort more relaxing for their anniversary. If you have any specific questions regarding the Yacht Club, I would suggest asking panelist Kay directly as she certainly is an expert when it comes to the Yacht Club!
Regardless of where you end up staying, you may want to keep an eye on
special offers on disneyworld.com. Another great website for Disney deals is
mousesavers.com.
Happy Planning! Diane :)