Time marches on. You need to be well on the way to producing your content elements. As discussed these may be filmed elements, stills, audio, text.
You need to think how the elements that make up your route are going to become discreet units that you can then add interactivity to.
That is you need to think of how to bundle the elements together. A piece of software developed for interactive story telling is called Storytron
Another system is called Korsakow

Its useful to look at how these sytems work. What assumptions they make and how they are structured.
The main site for Koraskow is Koraskow.org