I adjust my white balance constantly...I love custom white balance. If you have a grey card and the bag to bring it along, it would be best, but there are plenty of grey to white objects that you can white balance off of if you need to. I've white balanced off walls, pavement, people's t-shirts, clouds...whatever is handy!
I think because of the various show lighting gels, foliage, colorful paint on buildings, and varying sunlight, that Disney is a great place for using custom or manual white balance. Even the best Auto WB systems can sometimes get lost in certain situations.
Of course, if you shoot RAW, you can always adjust WB in processing...but if shooting JPG, you should try to get it as close as possible when shooting because the ability to correct in post processing is limited.