Jann --
Are you going to be doing the parks commando style? Lots of walking? Lots of swimming?
I'm a diehard Weight Watchers member and here's how I handled our last two trips. I ate very carefully for breakfast and lunch -- egg white omelets with veggies in them, fruit, salads with dressing on the side, vegetable soup, etc. Then, I let myself have a "treat" every night for dinner -- I ordered what I wanted (within reason, nothing fried, no fatty meats, nothing in creamy or buttery sauces -- otherwise, anything goes). And the real treat -- I ordered dessert every night! I didn't usually finish the dinner or dessert, but it made for such a great vacation to really be able to enjoy those meals with my family. And I lost weight on both trips -- a pound on our 5-day trip in May and .6 lbs on our 7-day trip in June.
I did do my regular workout at least every other morning while I was away and kept up with my water as well.
You won't have any problem at all finding foods anymore. I've noticed a big change over the last two years -- even the counter service places are getting more healthy alternatives. I had chicken caesar salad with the dressing on the side at both Backlot Express and in Tomorrowland at MK (can't remember the name of that big counter service place right now). Also had an awesome chicken salad with dressing on the side at Tusker House at AK and they have a cart outside the restaurant with all sorts of fresh cut-up fruits and veggies. And even if you want a burger or chicken fingers, you can always ask for fruit or veggies on the side instead of french fries -- the counter service places all offer this as an alternative. I'm sure you'll do great!