First of all, allow me to review some other reviewers: If you are "not in the mood for gloomy/sad" films for christmas or that christmas movies should be cheerful, then your review here is pointless: I'm not placing a review on red paint stating I actually wanted my walls blue either. A review should be about the film, not about a mistake the viewer made.
Having said that, this movie is outstanding and diverse. The score fits the fabulous scenery and sets that were created and makes it a joy for the eyes as well as the heart.
All actors did a good job in this, but the kids in this movie have no freaking business acting so well at this age. From the main actors to their best friend and little sister, all 4 of them were great at not only portraying the emotions, but showing them as children their age would show them, the only exception being some profound wisdoms the main character obtains and explains in the film, but that is an intended deviation due to the plot of the movie. It's clear the actors got the right instructions from the director.
The story takes great artistic freedom when it comes to events happening in it, but not an inch of fantasy when it comes to the realness of the emotions portrayed. It makes for a fine balance.
This film makes me proud and thankful for the dialogue that can be held around themes like grief nowadays.