There's no reason you can't start and do a few days of Ph1 before Thanksgiving. If you do eat non-Ph1 foods on Thanksgiving though, I would consider doing two solid weeks of Ph1 afterwards, and just consider this week a head start. You really need those two weeks to get you off to a good start. Or you can try to hold to Ph1 through Thanksgiving - just do whatever you think will work for you. You can have the Turkey and veggies. All of those other things you mentioned are about the same as far as causing cravings. Or you can go off a little and try to minimize the bad stuff. I plan to have salmon appetizer on tiny rye toasts, turkey, salad, sauerkraut, sweet potatoes, and veggies, and a sugar free pumpkin custard or apple crisp. All of those things are okay for Ph2. I will not eat the rolls, mashed potatoes, stuffing, or gravy. Good luck to you, whatever you decide!
Life's a journey, not a destination.
It's easier to stay on plan than to get back on plan.