Another thought is Sturbridge Village in MA, right off the Mass Pike. I know in the past they have done a "traditional Thanksgiving", but don't know if that still goes.

I like the New England states. My choice would be Boston because there is lots to do. You could even do a day trip to Cape Cod if weather permits. Mystic sounds good, and it is what I was thinking for myself this year. I was in Newport last spring and I loved it, you can not go wrong with any of these choices.I would keep it simple if that makes any sense.

Mount Vernon is open on Thanksgiving Day.

All excellent suggestions. Dad has actually announced that he wants to go to Front Royal, VA which seems to work well for all of us. I'm working on the details, but it seems like a nice workable destination.