I usually just allow myself one treat/meal per day. I have done the "I am on vacation and I am walking a ton" thing before and it didn't work for me. I didn't gain a ton of weight, only a pound or two, but, it was really hard to get back on track after our trip. Make sure to bring lots of healthier snacks, like almonds, cheese sticks, 100 calorie packs, fruit and carrots. I stick to my meal plans for breakfast and lunch. Then for dinner I will split something with DH, like the Monte Cristo, and have a salad and fruit. Or I will eat a few bites of the kids churro or ice cream.
It really helps my mind set. And I feel great when we get back from a 10 day trip and see that I lost a pound!