I didn't grow up with Advent calendars: my family was - at best - vaguely Presbyterian. Even when I married a good Catholic girl, I didn't get the whole 'advent' thing until much later. Like when we eventually had kids. (Don't ask how we didn't have them sooner - I don't want to imply any birth control flaws in her Catholic-ocity).
When the kids were old enough, we began buying the pre-fab cardboard calendars stocked with not very good candy, and the kids took turns opening one little perforated compartment at a time. Eventually, they grew old enough to get their own. Lego makes calendars full of molded bits of fun-sized foot-bruising toys for Advent, and we got them each their own.
This year, my Bride had the lovely idea to customize one, with hand-sewn little bags from scrap material numbered and hung on the windows, with daily treats like "one afternoon of making homemade gingerbread houses with Mom & a friend". And "one day of horseback riding together in the spring". It helps set the mood, and build up to the big day at Christmas.
And it looks pretty, too.