http://www.inklestudios.com/inklewriter – Inklewriter is a free online tool which would be suitable for the upper primary grades. Inklewriter allows you to create your own choose your own adventure stories. You can then read the stories and share them. Ir’s a great tool. My only concern would be ensuring that the children link all the story up. Remember that I would read and share some chose your own adventure books in class before I expected the children to be able to create one. By sharing the texts the class can learn the structure and features of these types of stories. I have added a tutorial below so you can see how the program works.