I second most of what has been said already: Tamales are truly tipical,
and should be had with some nice steaming cup of hot atole. For a more
formal kind of holiday dinner you may have Chiles rellenos or Chiles en
nogada with white rice. Also Chicken or Turkey mole or in Central
Mexico (Mexico City) they like Norwegian codfish (check this site:
http://www.elalmanaque.com/recetas/pascua/navmex.htm) is in spanish but
you can get some nice ideas there.
Raśl