Hi Darren, yay staying in Paris in December. This is going to be amazing for you and your family. Paris is magic as it is and staying in Paris just before (or during Christmas time) is going to splendid. We recommend the 8th district to be close to the main shopping areas as they put up amazing lights. It's also walking distance to most landmarks so you can enjoy your celebration time.
We stayed in the 9th district but for a very first time visitor, we do think the 8th district is the nicest.