There are several pools shared by the Dolphin and Swan. My kids aged 7 liked the Grotto pool. There is a waterfall they can go under and a slide. Not too big of a slide which was perfect for my kids.
Some rooms at the Dolphin and Swan have balconies, but they are more money. We didn't get a balcony. It's not important to us and we didn't stay in the room too much.
Compared to other Deluxe hotels I would say that the Contemporary has the largest rooms.
I don't know if there are any major differences between the Swan and Dolphin. I think the Swan has two sinks and the Heavenly Beds. I chose the Swan because it is smaller and I thought would be quieter. We seemed to walk alot over to the Dolphin (Cafeteria, laundry), that next time I might stay there. We had several large conventions staying at the Swan during our trip. First it bothered me, but I think it was good. Since most of the people were involved with the conference, the pools, restaurants, grounds, and transportation (boat & bus) were empty. It was also very quiet at night. No kids running up and down the halls or screaming like I have experienced at other resorts (including the Contemporary).