I used Close To My Heart's memory game cube. It has a strong magnetic closure and is pretty kid-proof. It comes with a countdown-convenient 24 cards inside.
So I came up with 24 things to do each day and decorated! A good old fashioned glue stick seems to work best with the chipboard. Plus it's cheap!
A little warning: when you first get this box all the squares fit inside with lots of room to spare; after you add a few layers of paper it becomes a pretty tight fit. If you are using all 24 squares, I would NOT recommend any 3D embellishments at all. They will not fit!
Maybe I should start my Christmas cards now...