I would advise against coming out Christmas. When I came out, I chose a time when things were calm at home and no major issues or events were going on. I also wrote a letter to my parents since they have always had a way of twisting my words or becoming argumentative when trying to talk to them. With a letter, what I wanted to say was on paper where it couldn't be changed or twisted by them. It also avoided a confrontation, leaving the door open for them to talk to me if they wanted.