Welcome to the club! Last year was my first gluten-free Thanksgiving. I made this chickpea pot pie and it was great:http://www.mittenmachen.com/2009/11/chickpea-pot-pie-at-maine-food.html
You can use whichever vegetables you like, and it freezes well, too. I made a stuffing out of wild rice, leeks, apples, and pecans instead of bread cubes:http://www.mittenmachen.com/2009/11/wild-rice-stuffing-at-maine-food.html
For dessert, I made a pecan pie and used Namaste brand gluten-free pie crust mix. It was a little more crumbly than a gluten crust, but it tasted good.
Other ideas for a main dish: tempeh or lentil shepherd's pie, broiled marinated tofu and chickpea gravy, winter squash halved, roasted, and stuffed with rice or quinoa or vegetables.
For dessert, you could always just do pie fillings a la mode in individual cups, without the crust. Pudding or mousse would be elegant.