Most important note: If you give the viewer a right to make choices they need to mean something, have consequences. Otherway they will not feel like their interactivity is really meaningful. An amazing example of great interactive films are those from the series LIFESAVER. The time pressure is stronger because we are in a mindset of saving someone's life. Also are decisions are VERY MEANINGFUL. Every decision and every second count.
This made me realize how interactive moving images can play an educative role. I also downloaded WhatIfI app that allows everyone with a smartphone to create interactive movies.