>I pegged what was going to happen in the episode immediately.
Yes, the storytelling paradigm it uses assumes you did.
>It is rather somber but that doesn't preclude it from being a kiddie show.
The fact that it airs at night, however, does.
Really though, while there are seinen series that could be easily mistaken for a "kiddie show" to the unobservant eye (e.g. Bottle Fairy), Shinigami no Ballad is not one of them.