If you are interested in a GoPro for your vacation, I recommend buying it early. Practice at home (filming and editing) so that when you get to Disney, you are in the moment and not fumbling with your new technology. It's not hard to use, but can become natural after some practice.
Take LOTS of footage. You never know when something magical will happen or you'll capture an awesome moment, and the more clips you take the better chance you have of quality clips when putting the final product together. For our 6 night trip this year I had about 300 clips. They weren't all used-- my over four hours of footage made for a pretty awesome 30 min video of our memories that we treasure.
If you have kids, and they will go for it, the child chest mount gives a fun perspective from their point of view.
Otherwise, you can do everything needed with a good short hand grip (get a wrist strap if the one you buy doesn't come with). As others have said, the longer poles and jaws/clip mount or anything to attach to a ride is no longer allowed.
Watch other people's videos on
YouTube and Vimeo-- there are many, and it shows you different perspectives and others' experience. I got ideas of shots or fun things to film for our trip by watching what other people had done and adding my own twist. I also learned different styles and what I wanted my video to be (or NOT to be).
It's a great, fun way to capture memories. My son asks to watch our video often, and I think it helps us all remember the magical trip details in addition to photos.