I went to Disney on WW twice, and did not gain either time. I LOVE the points plan and lost 65 pounds on it (took 18 mo) which I have kept off for almost 2 years now
OK:
Drink a LOT of water, and don't drink any sodas, smoothies, coffee drinks, slushies, etc. Those things have just way too many empty calories! OTOH, if smoothies are just a favorite splurge, you'd need to have one sometimes during the trip, but remember that there is SO much yummy stuff to have there-- save your points for the really great, really unique to Disney items.
Have low points snacks with you in the room-- granola bars, cold cereal, apples, whatever.
Whenever you eat, it HAS to be balanced. By following this rule, I end up eating mini-meals more and snacking less. Which is good. So- try to get some carbs, some protein, and some fiber whenever you snack. I *know* this is hard, but it will slow you down on lame empty calorie snacks, too.
Normally, I do not necessarily have a salad with every meal cause I'm not a big salad girl. At WDW, at buffets, I would scope them out, including dessert

and have a nice salad with little dressing (lemon, vinegar) or a low fat dressing that would seem most likely to be lower cal (study up before you go-- low fat raspberry vinaigrette can be very high cal b/c of sugar.) AFTER my salad and finishing a drink, I go for my food, and I am aware of portion sizes. Remember that the first two bites of ANYTHING are the most satisfying-- get two bites of everything that appeals to you. But JUST TWO BITES. Then, promise yourself you can either get seconds or have dessert.
I rarely had bread at WDW that was really worth the points. Watch out here.
If I have a danish for breakfast, I don't have any more sweets until at least 8- 12 hours later. This is just a personal Disney rule that I have seen to really help me.
Learn your portion sizes and STICK TO THEM.
That's my main strategy.... good luck!