I have been discussing this very same issue--the Christmas cards--over on my thread.
I don't have children and my H. isn't living with me right now. There are several people, distant relatives and friends who live far away, who do not know of our situation. Since we are truly in limbo, I wasn't sure what to do, either.
I decided to wait and only send out a card to those who send me/us one. Depending on how it is addressed, that's how I'll fill it out in return. Closer family members will send the cards to just myself, because they know. At least for this year, I think this policy will work best for me.
I think you should do whatever is comfortable for you. If you don't really want to let distant relatives know of your situation yet, then maybe just sign the family name "The Smiths" for example, or if that is too formal, put everyone's name on the card. It has to feel comfortable to you.
Happy Holidays, Hope
Most of us really marry only once. First love endures, even unto our dying day. And we never really divorce.