Your question reminded me of the one year I did an advent calendar with my oldest, I think he was somewhere between 3 and 3 1/2 years old and my daughter was an older baby. Anyway, we had an advent calendar that I made out of poster board or cardstock (can’t exactly remember which, doesn’t matter either would work). I had photocopied a nativity picture from our children’s bible and glued it to the middle. (It copied well as it was a line drawing). Then we counted down the days by adding a sheep each day. I cut out 25 blue circles out of construction paper (just traced around a glass) the front was blank – the back had an activity or the word “story” written on it. Each day we took down one blue circle and did the listed activity or read a story, then we glued a cotton ball sheep on the blank side of the circle and taped it back to the calendar. The sheep had black faces and legs. Not very realistic, but it was cute the border of cotton ball sheep!
I planned the calendar to be activity based. So on the back side of the blue circle I had an activity listed or “story”. So each day we did one Christmas activity OR read a Christmas book from our library. I recall that I had a few things I wanted to do (we made cookies for example) and spread them out over the 25 days, I also counted our church’s Christmas program as an activity, and the days we celebrated Christmas dinner with realitves. What was nice was doing the things I really wanted to, but also that it was flexible, so I could change the day we did an activity and I was able to see how much our family was doing – so I could limit it if needed. (Kids were after all pretty young).
The books we read were all about Jesus. I didn’t read any Santa books because at the time I really wanted my son to understand what Christmas was all about. I also broke down the Christmas story from our children’s bible over several days and read it the last few days right before Christmas. I was able to find enough library books about Jesus because I am blessed with a great library system, the hardest part was requesting a copy at that time of year. At this age, I also remember reading the same book several days in a row.
I hope that made sense and helps you come up with some ideas of your own!