Since 2008 Kelly Rossiter has written the Weekday Vegetarian column, starting with her introduction, on Moving Toward Vegetarianism. She wrote a terrific piece in 2008 on what to do if you are going veg and your family isn't:
Read her suggestions for dealing with the problem in On Moving Toward Vegetarianism: Thanksgiving
If your parents are traditionalists and you have become a vegetarian, not being thankful for the turkey can perhaps seem like a slap in the face to them. If your parents are indifferent or even hostile to your vegetarian choice, it can make for an extremely uncomfortable dinner.
Kelly cooks every recipe she writes about, then plates and photographs it, and since we are married, she feeds them to me, so I can attest that if a recipe is in here, it is guaranteed delicious. Try out here 2011 roundup: Weekday Vegetarian: 11 Tasty Recipes For a Meat-free Thanksgiving Feast
And from 2010, when the pictures were small: Weekday Vegetarian: 9 Thanksgiving Recipes, Tried and Tasted