We will be eating at the Yacht Club Galley on Thanksgiving. I have made 2:30 reservations. As we will not be in the parks that day I will probably bring a nice pair of capris and a somewhat dressy shirt. Or a casual style sundress (depending on the weather). My boyfriend, his dad and my dad will probably be in either some type of Docker style shorts or pants (depending on how cold it is) and a nice polo style shirt (maybe one with Mickey on it).
I am sure there is no need to dress up and if we were eating in the parks it would be a different story but as we will not be in the parks that day I do like to dress up a bit on vacation so we will be doing this. Great for pictures also. The GF is decorated so nice for the holidays. Make sure to check out the life size gingerbread house and the Christmas tree.
We were in WDW for Easter of 2005 and ate in the WL around 3:00. I had on a khaki color skort and a nice shirt. We ran into Mickey and Minnie in the lobby and they were all decked out in their finest Easter wear (along with Minnie's Easter bonet) - but most guests were very casual.
On a side note, we were in WDW last year for Thanksgiving and the few days before the holiday were COLD. We did an early morning Steam Train tour in the MK and were wearing jeans and fleece sweatshirts and were cold.
Have a great holiday,
Linda