Unfortunately the reality is not so idyllic. Thanksgiving can be stressful because of traffic, all the preparations and - well, because there are so many family members in one place.
When you think about family dinner you must not think only about turkey, mashed potato and cranberry sauce but about seating arrangement too. You don't want to put James near uncle Walter because they support different baseball teams. Michael can't seat next to any lady under 60 because his new wife is really jealous. And you will not risk having all the brothers together because this is a recipe for catastrophe.
When guests start to arrive you will not have a chance to solve all the potential situations because you'll have to take care of the kitchen, welcome arrivals, chit-chat to catch up... You'll simply can't leave your guests to choose the seats by their momentary inspirations.
Thanksgiving table cards will solve most of the undesirable situations. With properly allocated seating you just have to start the engine and enjoy your flight!