Everyone has there own idea of what constitutes a "traditional" Thanksgiving meal. If you are the hostess and plan on serving something other than the sit-down turkey feast, let you guests know this upfront on your invitation. This way no one is otherwise surprised when they sit down to eat.
If you are guest being served a less than traditional meal, whether or not you were warned ahead of time, you should continue to be a polite guest. Avoid an editorial comments about the dishes and make an attempt to try every dish you are offered.