Frictional Games should make a game like this

[hollowleviathan]

Children can be more frightening because there is an expectation of innocence and frailty. When a man becomes dangerous, that's less of a shock than a child becoming dangerous. A child is understood to be more simple than an adult. If a child behaves precociously, sees things adults do not, it circumvents more expectations of the viewers, and is thus more evocative.

In many ways you could see it as a crutch to support the story rather than an effective tool of scary stories, but I think it can be used powerfully in skilled hands, like the movie Joshua.

I think the point of the OP is that being scared is about not knowing what's going to happen. You can be scared of the monsters, but it's a more pervasive fright if you don't know where they are, what they'll do, when to expect them. Being off balance and uncertain of the future, except that it will be dangerous.