I liked this, it all made sense and there was nothing there that didn't need to be...a solid 4 out of 5 for me.
I especially liked the dialogue (between?) Joanna and Liam, this was a great red herring....and above all else, the script ended with a well built-up payoff.
You know what? I stopped reading halfway through to talk to somebody. When I got back I had pretty much forgotten the mum existed because she plays no part in the second half so my reaction was more an "oh, I see" instead of an "oh wow". Perhaps that's purely because I stopped in the middle but it might mean you needed either far more presence from her at the start or a bit of her near the end, though I can see why that might ruin it a bit too.
As I started reading this I was thinking it was just poor story telling and you should never show the mundanity of daily life. I was disappointed and expected better. Then I got to the end and realised why the beginning was like that, but I still think it might be worth dropping in some red herrings to make you think the story's going somewhere.
The priest's speech seems odd. What was he mentioning earlier if the family had yet to arrive and he was standing outside waiting for them?
Otherwise, it's about as good a story as you'll get into five pages, though I fear we've all now been jaded by the sixth sense.