We have just been. M, my mum, my sister, my friend and friend's DD (6) and my DD (8).
It was everything I hoped it would be. I read some very lukewarm reviews on it online before I left and assumed they were such because it is not a 'commercial type' Pixar related flick.. and am probably right and it really is very VERY good.
It is PG. The parts which some children (or more likely parents on behalf of their children) might worry over is the bit right at the beginning (before it re caps by a year) when Herrod is seen ordering soldiers to 'remove' all the baby boys and you see children taken from their parents and 'hurt' but it NOT graphic and you do not see exactly what is going on. In my opinion, any child who knows the nativity story would also know - or could be told - what Harrod did and why and so would be/could be prepared for this.
There is also (obviously) some scenes of childbirth, both Mary and her cousin Elizabath (poor women, devoid of epidurals as there were ! Probably the most harrowing (and very brief) scene is when Mary and Joseph, on the way to Bethlehem, pass a crucifixion scene. I explained to DD (in a quick whisper) that this is how they 'punished criminals' in those days and these were the men that Herrod was assuming to be the new King (before the Wise Men told hiom it would be a baby). Most children of DD's age and younger know that Christ died on a cross so would probably cope with this ok and again, it's not prolonged or very graphic.
The acting is very good and you get really caught up in the story. It brought a lump to my throat at many points. Really glad we went.
VERY good for escaping, for five minutes, from the whole commerical aspects of Chrsitmas which are all around and reminding children of the real nativity story in more detail than they learn at school. (Good for reminding adults too!)