I personally would make it a non-park day unless you are staying at an EP resort and can walk to EP or DHS (you couldn't pay me to go near MK on Christmas day). We were there over Christmas in 2015 and ventured into EP for a little bit and it wasn't bad (we were staying at BWI, so could walk over). Taking Disney transportation anywhere on property that day will not be fun. Long lines, lots of traffic.
Because we were staying at BWI, I made a reservation at Trattoria al Forno for dinner and we spent the evening at the Boardwalk and had a great time. While Trattoria wasn't very "Christmasy", it was very good and not crowded.
Where are you staying? If I could pick anywhere to eat in WDW on Christmas day (and I didn't care about traffic), I would pick Artist Point at WL. It is one of our favorite signatures - the food is excellent and WL is gorgeous at Christmas time. I would also uber there!