For the flight, you may want your vet to prescribe a mild sedative for your pooch. It may keep her a little more relaxed -- and we all know "relax" isn't in the definition of cocker spaniel!
For the place you will be staying - keep an eye out for ANY and all plants - pointsettia's are poisonous to animals, as are several other "holiay" related plants. And keep an eye out for chocolate - if there are going to be smaller children around, they often think that sharing chocolate with a dog is the best gift ever. They don't realize the danger involved.
I am glad you are getting to take your dog with you - I always hate having to leave my puppies at home when we travel & can't take them.