Bailey, try to keep up with exercise...it helps even when you might go overboard.
Try to be gentle with yourself...it's often tough in different environments to get the kinds of food you need and it's better to eat than to starve yourself in hopes that you won't gain an ounce. If you put anything on while you're gone, you can jump on P1 (if necessary) or back on plan at home, and it'll drop right off. I promise!
Disney is usually really good about posting menus online...or you can try using www.dogpile.com
or another search engine to find out if anyone has posted their nutritional information or 'dieting tips' for WDW. You can use that info to plan where you think you'd have the easiest time eating. Bring some food with you to make it easier...If you can bring a cooler, bring stuff...or buy when you get there. Cheese sticks, fruit, veggies that you can eat raw, WW buns for sandwiches...you can get a sandwich, then put it on your bread, instead.
Hope you have a great time...planning ahead will help you be successful on your plan!
But I'm with Ruth, though..what is the "dining plan"?