The smell of the environment is going to be full of new scents and also new faces. Some dogs may be excited to greet everyone while others may tend to be more timid. These are some measures that can help keep the dog safe.
If your dog can be anxious around large groups of people, a best solution is to create a safe space. This means having their food & water bowls in there with anything else that will help them relax. It can be hard for the visiting family members mostly children to not into the safe space. Teach them that when the dog comes out they may go over and pet without overcrowding him.
Thanksgiving tends to collide with emergency vet visits, due to dogs eating unsafe human food. But there are many that perfectly okay for the dog to eat during this holiday.