If you have the option, visit a local mobility vendor, and try out some options in person.
I have used both the "traditional" and the "Euro" style rollators, and you will walk normally. The main thing is to make sure that the handle height is proper for you. Every manufacturer will have their own instructions, but the idea is the same: you don't want to be stooped over, or placing your weight incorrectly on your wrists, arms & shoulders.
The main thing to watch out for is I had a tendency to really watch my feet at first, because I was so worried about tripping. Once I realized that was not going to happen, and I relaxed, I was fine!
This is one mobility category where a higher price point does not necessarily mean better function - I get the same use and value from an "old-school" traditional rollator as I do the "Euro" style. In fact, I actually prefer the traditional style when traveling because the underseat basket is better secured; the Euro style basket is out in front when you are walking, and is just a large zippered mesh pouch, where the traditional style underseat storage holds more, and is more private.
Patterned concrete will be a problem regardless of the walker/rollator style you have; I find that the larger wheels on some Euro style walkers are actually harder to use on heavily patterned pavement. A smaller, softer wheel does just as well, if not better in that case.
A rollator can be a great mobility tool for Disney World.