If you have not yet seen the movie, I suggest you do!
It lets you know you are not alone in your faith and love for God. In today's day and age, that is a message we all need to hear whenever possible.
The Holy Spirit sent a message, and the movie makers did their best to let God's word sing.
Do to subject matter I would take your children high school and up. It would be a great conversation starter, so they can understand what challenges awaits their faith outside your home's protective bubble (well maybe they are facing it is in public school already...)
Here is a link to the website so you can find out more, and a movie house playing it! God's Not Dead