Whilst in the pre-production stages of 'Children', Stewart had secured his film location in Montacute. However, at the last moment, he decided that he would change one of the locations. This was due to his desire to pay homage to where he grew up and where his film making passion began. Thus, within the opening scene, Shepton Mallet (Somerset) is seen. If you look very closely, when the title 'Children' appears on screen, the location is Shepton Mallet, furthermore, on the horizon you can see Glastonbury Tor - this was in honour of his Nan (who lives there).
Stewart met Aidan (the lead actor in 'Children') whilst on work placement - Aidan was acting in another production. After pitching the idea for 'Children' to Aidan, he wished to be cast as the lead character, 'Johnathan'. From then onwards, they became firm friends, this is evident, as they are working together on another film - 'An Unlikely Visitor'.
On the final day of filming, after a very early start, Stewart decided to cancel filming the final scene. This was to allow the cast and crew to have the evening off and would therefore shoot the final scene the next day. However, that night, a huge snow storm hit Montacute - making it impossible to film the next day. Therefore the issue of continuity arose, and the decision was made to cancel the filming of the final scene at that moment. Thus being in a rural location, this meant that it was almost impossible for the actors to get off the set, therefore, some had to catch trains home later that day. Consequently, this proved to be an expensive mistake, Stewart had to foot the bill a month later, as the crew needed to return to shoot the final scene which took just two hours to complete.
You may have noticed in the film that the notes that used were all handwritten. The reason behind this in the film, is due to Stewart's days at school - where him and his friends would write notes to one another daily.