With a bit of planning one thing would be to collect or buy from the dollar store some small containers and then stack them in a pyramid like a tree. Cut out a tree from large sheet to cover the front and cut "doors" where the drawers are. Inside the drawer are the supplies for an ornament craft. Only have as many drawers as you have days so doesn't need to be 25 just a couple weeks worth for Dec. Then each day talk about advent and Christmas coming and then make the ornament of the day to go home. Maybe tie it to the story of the day so if you read Rudolph the Red nosed reindeer story you would make a reindeer ornament. A note home to parents will let them know what you are doing.

From a cost standpoint the initial year it costs but then the boxes can be reused to count down to Easter with egg crafts or to summer or a special event.