What's open Christmas in Tucson?
I'm not sure, but for perspective on Tucson a fairly devout friend from DC--grew up in Tucson, with the devout stuff mostly coming later in life-observed: "You've got the only Kosher bakery that is closed on Sunday AND open on Saturday." We do have two Kosher restaurants, now, and I suspect they might be open on Christmas Day, but I wouldn't count on it. You might check back closer to December.
This is what was open last year on Christmas Day.
I suggest you read the Noshing Around column in the Tucson Weekly as that's a popular question and more and more people want to eat out on Christmas Day and not eat a multi-course buffet either.
Sabra, a kosher restaurant might be open. Several Chinese restaurants are usually open. Seri Melaka and Neo Melaka, Malaysian restaurants are always open on Christmas Day. And like someone else said, all the restaurant hotels.