Okay, I cannot speak for the Dolphin, but I think you will have an excellent time here. There CAN be a crazy wait for a table. Other times, for example when we went in January, we just walked right up and got a table straight away. Of course, we were lucky, as right after we got there, it got crowded.
Now, I must admit, the quality of the burgers has seemingly gone down. The burger used to be melt in your mouth amazing. I am talking money. Not quite the same experience in January. Now, it is still above the quality that you would find at many CS places, as I have found many a burger at WDW that is downright inedible. B and C is still better than most on property, and if you get it with cheese and bacon and all the trimmins', you are still going to have a pretty good burger.
I have seen in person and photos of the roast beef sub/philly cheesesteak, and it looks absolutely yummalicious. When I went in January, I had their onion rings for the first time, and they were awesome! I absolutely recommend substituting them for your fries. Or, buy some on the side for everyone to share.
The famous ginormous sundaes are definitely a masterpiece. But, they also have smaller portioned ice cream treats, like brownie alamode, strawberry shortcake, and root beer floats.
Again, I cannot speak for the Fountain at the Dolphin, but I think you would have a great time, and pretty good food at Beaches and Cream!