A lot of good suggestions, here - even for a shorter trip. One thing I might suggest, is to pick up a pair of walkie-talkies/family band radios to keep in touch with your fellow traveler. That way, if you get visually separated or one of you has an emergency/breakdown/needs gas, etc. you can keep the other one informed. Cell phones are good, buy you'll probably run into an area or two where you won't pick up a signal. Once you get to Disney, you can use them to coordinate lunch breaks, parking, leaving together, etc.
They also work well to communicate with your spotter when backing into your campsite on future trips. Works a lot better than yelling out the window, and many remote campgrounds have little/no cell phone coverage.
Have a great trip!