I have never dined at TI. But have eaten many Thanksgiving and Christmas dinners at Strip hotels.
What PJ said. How many of you will there be?
I'll add, don't expect the "special" holiday menu for cafe/restaurant to be like home (not where I'm from, anyway...they prepare food differently out west). Buffet may be best bet if you want to pig out, but get in line early.
As for it being Christmas, holiday decorations are worth taking some time out to look around. Bellagio Conservatory is a must see, but go early in the day, or prepare to be mobbed after about 5 pm. Millions of people with their kiddies, photo taking by everyone at every display. Feels like bumper cars. And that's before the holiday displays are set up!
Ven/Pal and Cosmo on the Strip have had ice skating shows in the past. Don't know about this year.
Good luck, and enjoy your Vegas Christmas.