I grew up in a large family, with multiple siblings and a Nana in the house. The necessities of that large family dictated several traditions, and then there were the ones we came up with on our own. I've already mentioned St. Nicholas Day, but there are other traditions worth observing:
—We never traveled. When your relatives all live in distant states, it isn't worth the hassle OR the recriminations ("You went to their place LAST year!")
—We went to Midnight Mass, which, of course, we young ones slept through.
—We were not allowed to open presents until Nana came out, and we were not allowed to bother her. Present opening therefore took place after eight or nine. (If you still have very small children, like toddlers, consider creating a reason why they can't open presents at 4AM. Make it an absolute prohibition, such as 'We can't open presents before breakfast and breakfast WON'T happen until the paper's been read' or some similar reason. Lie if you have to.)
—We received presents from our siblings, our parents, our Nana, and the Grinch. The Grinch's presents were usually silly.
—Stockings were not opened until after dinner. My parents reasoned that Christmas was a bit of a letdown after all of the presents were opened; the late opening of the stockings was a way to ease that feeling. Stockings had chocolate, small tchotchkes, and the like; nothing special, but fun.
Later on, other traditions accrued:
—Trolling for lights. The phrase is of my own coinage, and has been adopted by the family. It's not like I ever did more than simple bait fishing.
—Christmas wasn't always on Christmas. My sisters, who had waitressing jobs right after graduation, usually had to work on Christmas. My mother finally got sick of their being unable to come for Christmas and declared that she was making Christmas a day late, since neither had to work that day. Several years thereafter had arbitrary Christmas days.
—The water fight. It started when someone gave my father a SuperSoaker, and everyone else had little squirt guns in their stockings. Usually this was the guys' tradition, mainly because it was only the people who wanted to participate. Then one year my dad received a crossbow...
—Christmas bowling. This one was entirely accidental. My mom was looking for something to do one Christmas when one of my sisters had to leave early (and we had to open the stockings early as well.) She decided we could take advantage of the open bowling alley. We used silly pseudonyms, cried out "GOOOOOOOOAAAAAAALLLLLL!!!!" like World Cup announcers, and had a very silly time. The next year, we asked when the bowling was, having decided it was a tradition, much to my mother's surprise.