I don't really expect it to be an issue, since my family seems to specialize in dessert at these types of big meals. We'll have turkey, of course, but also some taters, green beans, corn in some fashion, rolls, stuffing, cranberry something and THEN we'll have pumpkin pie, french silk pie, raspberry pie, apple pie, cherry pie, probably a lemon cake, possibly angel food, cookies of some sort and likely some pudding concoction for the kids.
So I think you'll be plenty full, even without your tofurkey.
Did I mention that there are usually only 11 of us at these meals.