December 17-24.
We used to go Thanksgiving week. At first it wasn't too bad. More recently, it's gotten really crowded. Right now, Touring Plans is showing 8's, 9's, and 10's for Thankgiving week.
We then switched to a few days before Christmas, checking out on December 26. This was crowded but not as crowded as Thanksgiving week had become. Right now, Touring Plans is showing 4's and 5's for the week before Christmas. Christmas Eve is a Saturday. This is showing a 10.
Consider a subscription to touringplans.com to see their projections in detail.