I gave my students an outline to an optional project about three months ago. The task was to build a model of a famous place out of 100% recycled materials (paint and glue were the exception). The other catch, you had to include as many members of your family as possible in the construction. Here are the final results.
I have had many happy emails from parents telling me how great it was to work with their child on a creative project.
This was not connected to anything we are studying in class, and it was 100% optional.
Sometimes we don't need reasons to do something. Sometimes we do things just because they are fun or engaging.