I think neither of these games are really 'kids' games. I don't think kids are the main target group, kids can't really kickstart anyway. Sure, there are some funny or even ridiculous things, like the sneak animation, but the core of each game is not light heartly dogood stuff. It surely not Super Mario RPG or anything like that. Following Sebilles story is surely pretty tough and dark, same goes for all this soul ripping source stuff. But at least here you can fight those evil magister and try to help people, or you can be worse than them and just slaughter everything.
But honestly, seeing and knowing what is happening in the real world is far more traumatizing and often on a daily base, if you don't mimikry the three monkeys. So I do not have really an issue with the darkness, it still only a game and here you can try to fight the evil. It's still softer than for example Wasteland 2.
Your first main event there forces you to sacrifice one of 2 towns, because you can't save both.
