Reporters or more particularly editors are obsessed with age/colour etc. It helps, they feel, to enable their readers to "identify" with the people in the article. It's known as "human interest".
In this case I would say that it is relevant as the reason the boy was in the shop was that he wanted to legally buy his first lottery ticket and his father, for who he worked part time, had given him the day off to celebrate his birthday and this little trip was part of the lad's personal celebration. Equally relevant is that the following day was to have been his last day at school. All things that a lad of that age would have been looking forward to. That his "special" weekend should have been so tragically curtailed is particularly poignant.
So whilst I agree that often age is not relevant to the report, in this case I think it really is vital if the story is to have any impact on an increasingly blase readership. These additional details, together with the brave and Chrisitian way in which his family have spoken about their feelings, have certainly made me personally take more notice of the story.
I have not dismissed this as "Oh another fvckin' little scrote getting into bother and paying for it ~ serve him right" because this is just so plainly a nice lad from a decent family going about his lawful business, with everything in the world to live for and this happens to him. Without the details, age, church, family, last day at school, apprenticeship lined up to start, his murder would have meant nothing to me. Now I feel bloody angry about it and determined to bend the ear of my MP to try, in my small way, to do something about the society in which it could happen. It also brings home to me just how random these things are nowadays and that makes me fearful to let my own children out of my sight.
I shall now remove my editor's hat.