We haven't had a tree in my immediate family since I was four. We celebrated a version of Christmas until my sister and I were teens and were old enough to understand why we didn't really "do Christmas" like everyone else did. Now that she and I are grown and married with kids, we have our own holiday traditions, but still don't have conventional celebrations, and neither of us will allow a tree in our respective homes.

One of the traditions that my oldest and I started together was to visit holiday light displays. They're pretty, the kids like them, and I feel as though they can be viewed as pretty lights separately from paganism. Another thing is that we pick as many angel tree kids as we can afford that year, and we buy gifts for them. They have so much fun picking out things for another child, and I really feel that we can do it separately from paganism (if I stumbled across an angel tree any other time of year, we would still do it). Also, we do try to have a meal with extended family between Thanksgiving and Christmas; the family fellowship is nice even though they all think we're a bunch of weirdos for not celebrating Christmas and Easter and not taking our kids trick or treating and whatnot.

Good luck on your journey!