From the site: "Storybirds are short, art-inspired stories you make to share, read, and print. Read them like books, play them like games, and send them like greeting cards. They’re curiously fun." I like the looks of this site, but I've not created a story, so I can't speak to the difficulty. It's free and you can set up a class.
Write it on your communicator: storybird.com.
Extra credit: storybird.com/teachers/.