Be sure to read up on Information on the First Thanksgiving. The first Thanksgiving was a celebration of the first harvest had by Pilgrims in the US, and was a festival with the 50 or so Pilgrims plus just under 100 native Americans. The food therefore was a mix of what the English settlers knew about and/or brought with them, plus what the native Americans brought in to the feast.
A letter written by one of the pilgrims mentions that they served venison (wild deer) and wild fowl - probably turkey, duck, and goose. Rabbit would also have been served. Other traditional items served at an English feast would have included cornbread and pudding. Cheese was a tasty treat. Vegetables would have included corn, onions, and pumpkin. They did NOT eat corn on the cob at the time; the corn was only suitable for dishes and meal. Fish was usually not served at great feasts because it was too "common", but there might have been some lobster or cod.
Note that the first Thanksgiving would not have had sweet desserts, and there was no popcorn at the time. Feasters were usually too stuffed by the end of the meal to think about eating anything else!
As you might imagine when cooking for 150+ people, the meal was not high on intricate cooking. However, the food was very tasty, as both the English and the native Americans knew about how to plan for large parties. There were no forks at the time - just knives and spoons, and plates were usually wooden.
Here are some suggestions for recipes with a 1600s flair. Note that the early pigrims did NOT have pigs so anything involving ham or bacon would be inappropriate. Also note that cranberry was not introduced until many years later.
Cornbread - admired by both the English and Native Americans
English Cheese Pie - cheese was important to the English
Venison - five deer were brought by the Native Americans
Wild Turkey - Native Americans and English alike enjoyed this meal
Garlic and Onions - staples of the diet
Pumpkin Pudding - there wasn't pumpkin pie at the time
Indian Pudding - can be served as a warm or cold dessert
Information on the First Thanksgiving