Celebrate Thanksgiving!
Although the Thanksgiving holiday appears to be a non-religious secular event, there is a possibility that its origins are idolatrous in nature. To utilize the day for a family get-together is certainly permitted. To serve Turkey, if that is what they wise to eat is “Not Strictly Forbidden” “But” may fall under the category of those things which Chazzal (our Rabbis) viewed with disfavor, as it appears to follow the custom of the Gentile. Furthermore it is also possible that celebrating such a private holiday may be forbidden from the Torah Law. (Mishneh Halachos 10:116)

Summary: One may utilize the day for a family get-together and serve Turkey but must keep in mind that its only the Mitzva of:
Inviting Guests.