Wow! This thread is a year old! LOL!! It sounds like you are off to a great start. Epcot also has Future World which can be a study in itself. No need for preparation really. There are all kinds of physics experiments and Wonders of Life is great for biology challenges. My kids (dd 10, dd7, ds4) really got a lot out of our trip.
And don't forget AK! You could do a study on the continents of Asia and Africa, what kind of animals are there, what the climate is like and why Orlando is a hospitable place for those animals (you could talk about why this park wouldn't work in Nebraska or Maine) We love love love AK! I think our kids get as much from that park as they do from Epcot.
One thing that we do is take the time to talk to the CM's, especially those CM's that are not from the US. We go to WDW in the Jan/Feb time frame and so we don't have the crowds and so the CM's have more time to sit and talk with you. If you mention that you homeschool they seem to open up and tell you more than the average kid. We had a very nice lady from Pakistan tell us all about the village that she grew up in and how it was different from the city that we live in. We sort of did a comparison thing like, "We watch TV at night." "We told stories about our ancestors."
And don't limit your talking to just the CM's. We have found that most of the people from other countries or cultures are very open to talk about where they are from or what they believe. On our last trip we passed by a Jewish gentleman with his hair in curls (prayer curls) wearing a top hat with Mickey Mouse ears. There he was with his prayer shawl showing, wearing dark clothes, looking so "proper" but with Mickey Mouse ears. We all burst out laughing and he started laughing with us and he winked and said to my oldest dd "You think that I should wear this to temple next week?" Which of course made us laugh even harder! He then took a few moments and shared with us that even though people of his religion seem stoic and serious that they enjoy having fun just like everyone else.
2 years ago we were on the monorail with a woman from India who was in a sari and had all kinds of jewelry on. My oldest leaned over and asked me why she had a red dot on her forehead and the woman struck up a conversation with us about what all her "regalia" was about. Her different pieces of jewelry, her dress and yes even her red dot.
We try not to do much other than journal when we go. Last year I was obsessed about making sure that my kids would "get a lesson" from our trip and what I found out was that I didn't have to do all that much work. They naturally "get it." Somedays we will be working on something and one of my kids will say, "Oh, that was like 'da-dee-da' when we were at Disney." So they do get it even without us even having to put much effort into it.
But I like your idea of using Disney as a catalyst to your curriculum. Think we should get together and do a complete "Homeschool Your Child with Disney Curriculum" and get really rich (and afford all the trips for our "research")?