Christmas in Nice

You've left yourself a bit short on time for Christmas dinner. All the hotels will be filled, for Saint-Sylvestre and the Reveillon.
Here's what to expect: Pay attention to the closing hours.
http://www.nicetourisme.com/agenda/evenement/7908-reveillon-de-la-saint-sylvestre

Chexbres has answered for New Years, but same thing for Christmas. You need to go on line and reserve for the evening of the 24th and Christmas lunch. These are big special meals. Otherwise, you can walk around and you’ll probably stumble on a Turkish kebab place or a Chinese to fill your tummy. However, the Christmas meals are important part of the culture and worth participating.

What’s open? I don’t know because we’re usually with the family just east of Nice, but will go over to a Christmas market or along the beach, bundled up, later in the day after the gargantuan meal.

Thanks for the info.

Yes, you should make reservations in advance. The app/website The Fork/La Forchette can help, if you don't want to call around. It clearly is a subset of what is available -- and even there there is not too much left. The hotel restaurants will be open as well. Be aware that many of the places may have a special set menu, at a higher price than normal.

Or, if you are staying in an apartment, you should go to the supermarket or outdoor markets.