I recently bought a set of food safe markers (kind of like these) and we've been having fun decorating our food with them. On this particular day (which happened to be Emily's birthday), we decorated circles of fondant to put on top of cupcakes. This was a really fun activity for the girls, and a lot less mess for me to clean up than when they are allowed to use sprinkles!
the cupcake I made for Joel:
Emily's cupcake is the one with the 3 on it (I used a fondant cutter, she did the coloring):