I let myself relax a bit while at Disney last February, and came home about the same weight (no gain).
We were on the old Silver Plan, and used a few of our Wishes on nice big meals, but I was very careful about how much I ate. My rule was to fill up a plate with fruit at any buffet, and eat that before hitting the other parts, and finish any salad or veggies that were a part of my meal before trying to finish anything else.
If I was full, I stopped eating. Period. Even if that meant I had only taken one or two bites of my dessert or entree.
I was very happy to see fresh fruit available at the parks for snacks. A frozen banana counts as fruit, right?
When I calculated the amount of activity points I'd be earning (like, 10 per day at least?) I figured I'd be ok.