What hotel are you staying at? If you are staying at a Disney resort (or Universal for that matter), take advantage of the early access/late access to the parks.
What do your kids like too? Are they thrill seekers? Are they into shows? Music? Animals? Learning? (I am!). Speaking for Disney, you probably want to only spend a day or so at EPCOT. There is lots of very interesting stuff, but there is a bit of a learning aspect to it (still fun) and geared more to adults. Magic Kingdom might seem full of younger kids too, but you came all this way! Why not see the Mouse?
Another great tip is to start thinking about if you want to get reservations to eat somewhere.
Let me know what your plans are and what you want to do!
As for food, depending on your budget, and how much you like fine dining in theme parks, you will need reservations. Some restaurants are booked months in advance. Typically, my family will make 3-4 reservations for nice restaurant, splurging on one, and erring on the cheap side for the others.
...more to come...
Before booking a restaurant, read some reviews (either here or elsewhere) and tips regarding a specific restaurant. Not all nice restaurants need reservations. And don't be afraid to look at the restaurants at the Disney hotels.
For Universal, I have found (in my one recent trip to Universal) that reservations made before you go aren't needed even for Mythos on a weekend. Though we did get them the day of (or day before, I forget which).
I'm not experienced at all with fine dining at Sea World.
Walt Disney World
Tokyo Disney Resort
Theme Park Insider Books