As a suggestion on music/BGM... not sure if you'll use it or not, up to you... When you get to the part where they time travel to the past the first time, or at least for the ending credits... Huey Lewis & The News - Back in Time, A soundtrack from Back to the Future.
http://www.youtube.com/watch?v=A2hePcR50v4
And it's just a suggestion. You don't have to use it if you don't want to.
