I'm with those who say they aren't going to get uptight about eating over the holidays, but I do it with a caveat: I try my best not to skip an exercise class, but even more so make it a part of the tradition to take a walk after a big meal. Instead of driving around to see the holiday decorations, walk and talk. I've spent holidays in Hawaii and in Florida and in Virginia, and all three places we took beach walks after the heavy meal. Here I have a hard time getting people to get on the bandwagon for it ("Oh, no, let's drive" for walks that aren't difficult or long). But you can start with, "OK, I'm taking a walk, anyone want to join me?"
For those of us who truly love food, thinking that we're going to diet our way through the holidays, or make certain dishes without the special ingredients that make them, well, special ... well it isn't going to happen. In my experience the anxiety that comes with knowing you blew it just makes you eat more. So, to me it is enjoy, but keep moving. And I don't care what anyone says, cleaning house and cooking don't burn a single calorie (yeah, I know, I know ... but somehow I know many, many families where the couch potato members are thin and the run up and downstairs, cook the food, do the laundry and dishes members have weight issues).
The walk theory has a large, very positive, side effect. Even when the weather sucks, getting out for a bit every day, on your feet, staves off depression, a really terrible side effect of holidays.