As an ex-catholic and now happy unbeliever/humanist I suggest...

As an ex-catholic and now happy unbeliever/humanist I suggest you read few recent bestsellers on a subject of evolution/religions before you embark on your journey of making movie/book. You do not want it to be a complete dud, do you?
Religions/beliefs were always men made. There are thousands upon thousands of gods/goddesses who are not even a memory any more. Their temples in rubble and their holy scriptures and books just items in museums or forgotten in some other places.
The authors I would suggest for you to pick and choose from are Richard Dawkins (a must read!), Sam Harris, Daniel Dennett, Christopher Hitchens.But there are hundreds others equaly interesting.
To help you with writing some scripts please feel free to ponder on this small collection of famous sayings/quotes of our greatest free thinkers of past times. Whatever you do, please do not push the creationist rubbish into our society. We do not need more ignorance but less.
It is very hard to educate young minds with their parents stuffing all sorts of nonsense into their developing brain cells all day long when they are at home. Let us know when your masterpiece is ready to be viewed.

All thinking men are atheists - Ernest Hemingway
The public will believe anything, so long as it is not founded on truth - Edith Sitwell
Only educated are free - Epictetus
A myth is a religion in which no one any longer believes - James Feibleman
The more I study religions the more I am convinced that man never worshipped anything but himself - Sir Richard Francis Burton
The Devil has supplied so many services to the Church, that I wonder why he has not yet been sanctified - Carlo Dossi
Religion is a disease - Heraclitus
The religion of one age is the literary entertainment of the next - Ralph Waldo Emerson
There is in every village a torch, the teacher and the extinguisher, the clergyman - Victor Hugo