Members of the Washington Calligraphers Guild were asked to participate in a Family Fun Day at the Walters Art Museum in Baltimore as part of the celebrations around the exhibition of the Wisdom Books of the St John's Bible which are on display there until the 24th of May http://www.thewalters.org/exhibits/saint-johns-bible/index.html
The exhibition also featured sacred texts in different languages (and different religions). So I offered to have a table where the children could make up their own alphabets. I gave them sheets of paper on which they could design their codes and then had little books made up in which they could write a story in their own code with the code itself on the back page. It was a slightly difficult task but a surprising number of children took the time to design their own code - no one actually made a book but some took them home to finish. Since it took me at least 3 days to do this exercise I wasn't really surprised. The stones are collaged Japanese paper attached with double stick tape.
Here are links to PDFs of my book design and code page in case you have any children who are interested in this project!
This one is from Paul Johnson's Get Writing book. http://www.johnnealbooks.com/prod_detail_list/19
Use the directions in the 4-page origami book for this.
Use this page to design your own alphabet.