I recently went on a five day cruise and was just as worried as you are. I tried just about everything from the multiple food buffets and restaurants, and yes, that includes sweets and desserts, but I balanced it out by having salad, vegetables, eggs, and tomato-based pasta when the options were available. I ate a lot in five days (I mean A LOT) but because it was more of a constant grazing, it didn't do me too much harm! I only went back for seconds once or twice, and that was usually only if my mom had something on her plate that I had somehow missed and thought looked good!
Anyway, the point of that story is, I definitely gained some weight, but the day I got back I went right back to my usual WW plan and managed to lose it within 2 weeks. Don't stress out too much (the weeks leading up to the cruise, I REALLY worried about it), and obviously make the best choices you can, but ultimately, enjoy yourself as much as possible and if a great vacation results in a gain of a pound or two, you KNOW you can get it back off again because you've already lost 40 lbs (according to the numbers beneath your avatar) and that's fantastic! Even if you don't track your points while you are on vacation, you may want to still consider writing everything you eat down, as it will help you reflect on your choices and think about what might be a better option for the next day or the next meal out.
Have a great time!!