We have just found that our traditions come out of things we all like to do. Sometimes I don't even know we have a tradition until DS points it out ). For example, whenever we get back from a trip, we always have Kraft Mac and Cheese because I always have it on hand, not because I thought of it as a tradition. It was something I can do while we're unpacking. When DS was about 5, I had a little more time (and food on hand) and so I started to make something else for dinner. He had a fit, because we always have Mac & Cheese when we come home. I realized he was right--we did have a tradition, and apparently one that meant a lot to him!
The big traditions are Saturday morning breakfast (pancakes or waffles) and bedtime stories (which are continuing now even at 12, although the books are hardly kids' books anymore).