Congrats on the 20 lbs. I'm a Pooh sized woman going through menopause no less so I know how hard it is to lose weight. But as others have posted, you're on vacation and the walking will more than make up for whatever you eat as long as you eat moderately.
About MS, I went on this past Sept. and my main concern was that everyone said it was so cramped. Well I loved it so much I went out and got on line and went on again. Its not has cramped as it appears once you are seating inside and if you keep your eyes on the screen you should have no problems. I like the weightless feeling so I enjoyed this very much.
I also did the Shark tank at Typhoon Lagoon and believe me you will not be only "Pooh sized" person there so, relax and enjoy yourself, you'll be in the Happiest Place on Earth!!
Have a wonderful trip!!