Hehe, I asked something similar early on last year! I asked very late though and our holiday wasn’t nearly as long.
From our experience of the parks, Universal’s Islands of Adventure was the clear highlight for the variety and the surprises. The water rides there were so much fun with family in the hot Florida climate. I’m not a big fan of Harry Potter either but all that stuff blew me away. Very creative and wonderfully crafted.
Of the water parks we preferred Disney’s Blizzard Beach to Typhoon Lagoon (Universal’s Volcano Bay wasn’t open then). I’d like to have seen the new Avatar area too.
Epcot is definitely worth a visit if you get a chance, put a day aside to explore it properly and enjoy the food and drink. The lake lightshow at the end is really cool too.
Our trip was short and full-on so we didn’t stray too far from the parks. Ripley’s Believe It or Not was amusing and 'gator spotting on a Boggy Creek airboat ride was an interesting experience, and loud!
Hope this helps.
Edit: oh, I summarised my trip at the end too, with some pics.