To me, holidays are family time. And his kids need that. Not to say you don't need it as well, but you are old enough to understand that it is jsut another day (technicaly), kids aren't. Make whatever day you can get together, your holiday. Make a special meal, do the present thing, whatever traditions you want to have together, do them, on your special holiday.
On the other note- my uncle stayed close with my aunt when they split for my cousins sake. And honestly they make great friends, but terrible relationship material. He's had issues with g/f's understanding that he goes out with his ex wife and her husband, that he stays the night there from time to time. But he's also had some that have totaly understood and supported it. I understand the dynamic there is a little different, but it is possible for it to work out on the positive side. My cousin has grown into a well rounded young man b/c he's seen that even though they can't be in a relationship, his parents still care for eachother, and him.
Not saying you should run out and be best friends with someone who stalked you, but it shouldn't make you feel anything but proud of him for being in his kids lives. It's not a reflection on you, it's a positive reflection on him. Like I said, holidays are just another day on the calendar, it's what you do on them that make them special. So make your own holiday together. Make January something or other "our christmas". Or "our new year" and do a countdown and the whole bit.
Karma and I are often apart on new years, so we've started celebrating the pagan new year (halloween) together. It's "our new year". We toast to it and all.