I think that it would be better to just *SLIGHTLY* cut your calories the day before and after-having 1400 a day if you normally have 1500, etc.
The day OF Thanksgiving, then just add the 200 calories that you took from the day before and after, and maybe add an extra 100 for the holiday. So if you normally eat 1500 a day, that day would be 1800.
It would only be 100 calories more than you would normally take in over the course of the week.
Also, have a slightly lower calorie breakfast, so you have a tad more to play with at lunch/dinner. Just small switches during breakfast, like having a 45 calorie or so cup of berries instead of a 100 calorie banana, etc. can do quite a bit.
Just watch portion size, and I don't remember where I read it-but advice that I follow is to look over the food, and spend the calories on only what you REALLY want. Mashed potatoes are great, but are often out there year round, so why use the calories on them-when your Aunt Betty's pie/dressing is only around once a year? That sort of thing...
Also, look online for lower calorie desserts, and make one for the occasion. You can reduce the fat and calories in pumpkin pie by using the fat free condensed milk instead of the regular version, and it doesn't affect the flavor. Eat pie that only has a bottom crust-double crust pies are more caloric in general, etc.
I for one, am going to two different places on Thanksgiving. I am planning on having roast turkey, a vegetable, and one small portion of "must have" food while I am there....and at the second place, I am having one small portion of the dessert that I like best. That's it. I am not eating dinner twice.

I am not eating 3 different desserts.