A number of holidays merit special buffets in Las Vegas, though except for the handful with traditional foods, the most notable element of holiday buffets is the higher price.
Thanksgiving, Christmas, St. Patrick's Day, and Passover buffets feature special fare, while New Year's, Easter, Mother's Day, and Father's Day often serve higher-quality food in general, without any specific holiday dishes.
Thanksgiving buffets offer up some combination of roasted turkey, stuffing, giblet gravy, cornbread, candied yams or mashed sweet potatoes, cranberry sauce, green beans, pumpkin pie, and spice cake.
Christmas might feature roast turkey, prime rib, and ham, plus traditional sides like green bean and mushroom casserole, mashed potatoes, and sage stuffing, and fruitcake and Christmas cookies; egg nog is sometimes available.
St. Patrick's Day foods include corned beef and cabbage, shepherd's pie, Irish soda bread, and of course green desserts and beer.
Passover buffets were served for many years at Station Casinos' Feast and Festival buffets, at no extra charge, during the eight lunches and dinners of the spring Jewish holiday. Food included matzoh ball soup, brisket, potato latkes (pancakes), matzoh brei (matzoh and fried eggs), tzimmes (sweet root veggies and fruit), and charoset (apples, nuts, and wine). But most of those buffets closed and aren't expected back. Only one, the Rampart Buffet, might do Passover again.
You can check with the individual buffets at holiday time to see what they're serving and how much they're charging.