We usually drop our bags in our room, and head to the muster station, it takes a couple minutes for them to scan your sea pass card. You’ll need to watch the video first though.
Cruised on EC in Aqua at the end of August , we were told we could only order the daily things (french onion soup, shrimp cocktail, etc) from the MDR. If we had a dietary restriction, our waiter said he would check with the manager to accommodate us.
YMMV but I would mention your wish for the traditional Thanksgiving menu on day 1, so you can make other arrangements if necessary.