I do an activity advent calender with my kids each Christmas. I love it. In November, I think of all the things I want to do in the next month, write them down, assign them a date on the calender, and get the materials I need. I think I'm being very organized and the next month will proceed smoothly. But, inevitably, something comes up during December where what I had planned for that day just can't happen. Maybe the activity I had slated for the day was too time consuming and I had a busy day, or company unexpectedly shows up for a visit and I don't have the supplies for all the extra kids, who knows. The point is, there needs to be some flexibility in the advent plan.
This year, I discovered a great way to fill an activity for the day that doesn't take a lot of time, and can accommodate any number of people, so you can keep it in reserve for when you have to adjust your original plans.
It is a game called Pass the Parcel. All you need is a prize, (preferably something everyone can enjoy together so there is no winner and loser at the end, thus avoiding hurt feelings) wrapping supplies, and a dice. You can even call this a 'learning game' if you wanted, since it involves number recognition. Ideas for group prizes: a new Christmas video for the family, a box of treats, a new book to read together, a package of finger puppets, a puzzle to build, supplies for a craft, etc.
Step 1: Wrap your prize in layer upon layer upon layer of paper. I think I used ten this year. (You can do this in advance and tuck the prize under your bed until that busy day creeps up on you. Then you are prepared!)
Step 2: Get all the participants into a circle.
Step 3: Roll the dice. If the player rolls a predetermined number (we used 3, but it is just whatever you pick) they get to start unwrap the gift.

Step 4: The players keep taking turns quickly rolling the dice, trying to get the set number.

Step 5: When someone else gets the lucky number, they get the gift and start unwrapping as fast as they can.

Step 6: Keep rolling the dice, and passing the parcel accordingly, until all the wrappings are gone.

Step 7: When the gift is all the way unwrapped, enjoy the prize together.