Dolphin swim is meant to be fab but is expensive. You can als book breakfast with Shamu at Seaworld.
Don't go to WDW at the weekend. Get there very early. It takes half an hour to get from your car to the gate. Buy tickets beforehand. When you get through the gates - RUN. Do everything you possibly can & get fastpasses before lunchtime. It gets the most busy just after lunch then things get a bit quieter after the 3pm parade when a lot of people leave.
I'd suggest you do as much as you can before the crowds get intolerable, get your hand stamped, leave for the afternoon and then go back in the evening. If you watch an evening or electrical parade before the park closes make sure you are right by the exit as there is always a terrible bottleneck to get out and the monorail has terrible queues.
If you like fast rides go to Universal and MGM if you don't stick with Seaworld and Animal Kingdom.
Cypress Gardens is good (40mins south) and has a big new water park next door and the crowds are not bad either. It's all new as they moved.
If you want to do a themed breakfast go to Chef Mickeys on the 4th floor of the Contemporary Hotel. Well worth it. Book before you go as it is very busy.
If you have girls the Cinderella themed dinner is lovely at the Grand Floridian hotel, again book in advance.
Boma restaurant is great at the I think Wildnerness Lodge. African themed but the most tasty food we had all holiday.
Get yourself a book called The Unoffical Guide To Walt Disney World by Bob Sehlinger it is our holiday 'Bible'. Lots of suggestions, phone numbers, ride descriptions.
Do not miss The Lion King show at Animal Kingdom and the Kali River Rapids are great fun too. If you want to travel further Busch Gardens in Tampa is wonderful.
Also don't forget to go to the Disney built town called Celebration, it's off the 192 in Kissimmee. A lovely old fashioned (but new) town built around a lake. Lovely affordable gift shops, restaurants, cinema, fountains for kids to play in. Great for an afternoon. There is a wonderful doll and teddy bear shop there and a kids clothes shop (dearer than usual but different).