A.C.
We also do the Jacquie Lawson calendar; my father sent it over for the boys. We've been following along with that some--we made a figgy pudding on the day it showed the recipe and how to do it. The boys played with the snowflakes game on that site (I was very very surprised at how artistic my 4 year old is with that), and then we set aside some time to do cut out snowflakes with paper and hung it on our windows (I got the idea from the Lawson calendar but had to get on the internet to figure out how to do it for real---hadn't done it since I was like in 2nd grade). We played a new game together as a family, we have certain things we do "traditionally" on certain days: this day we decorate the house and tree, this day we watch this Christmas movie, this day we bake/decorate cookies, stuff like that. Every year we go to the big parade downtown on Black Friday, see a local production of The Nutcracker and visit Santa and see his reindeer, participate in our community holiday festival and toys for tots drive, we adopt a family for the Angel Tree, we do other fun stuff as we find it: ICE, a special event at a historical village, a popcorn stringing party for the kids with a neighbor and her kids (the dog ate it but it was fun, lol), a cookie exchange, a couple potlucks, 3 birthdays, some more concentrated time to work on cub scout badges/belt loops during their days off school, impromptu fun like going to play if it snows (or in our case, it iced and we rode boogie boards down the slopes at the park....a southern version of sledding). There's always a play to check out, sometimes a dance, etc. There's lots you can add here.
I like your idea of an activity advent, especially adding good deeds. My husband saw a man that we suspect is living in some bushes in a field, and he was terribly underdressed for recent icy weather (pj bottoms, flip flops, a ripped coat) but when he went to speak to the man, he had disappeared. He was upset and told me about it, so we put together a drawstring, waterproof bag for him with soaps, a 9 piece toiletry kit (what you see in the travel section of stores), some good leather gloves, a winter cap, a pair of socks, thermal underwear (pants and shirt), a hoody, and my husband's hiking boots that he'd replaced with newer ones a couple months ago, and some nonperishable snacks we had in the house (cliff bars, nutrigrain bars, nuts/dried fruit, pb crackers, and a 1 liter water bottle that he could refill if he wants), and then my husband sought him out to give him the gift....and an extra jacket (Jeremy's been the same size for 20 years, and never throws clothes away).
I think anything you do during the season could be incorporated into your calendar, just do it with purpose. Like a special day to do specific shopping, or to write letters/fill out cards, take a fun picture together (even if a neighbor has to take it if you don't want to go to a portrait studio), go to a community event, make cookies or some treat together, go see Christmas lights, there's SO MUCH that goes on around here during the year. I'd look at your community calendar for the month and incorporate some opportunities there into your advent. Sounds fun!