Do you remember making paper fortune tellers when you were a kid? You'd flip the the parts back and forth and unfold it to discover your fortune.
This has a PDF file to print, but I think it would be even more fun to get the kids to draw the hearts and numbers and write the messages inside. All you need to do is cut the end off a piece of paper to make it square and off you go! Children who are too young to write can help by colouring in the hearts, or even decorating the paper with bright crayon scribbles.