Well, I partly agree. I don´t think that this setting should be filled with a lot of dangerous monsters that can hurt the kids. What I´m suggesting is, just like you say, more something about many kind of obstacles, where "monsters" (like dinosaurs, robots or dangerous aliens) are just some possible options. Many types of antagonists – also very human and mundane – are possible! Since this is a game partly about more hidden back stories, perhaps some bigger conspiracies (different from each other) could also be a part of a "Bestiary".A small guide would be fine, especially with some cool art, but as this is not meant to be a high combat game my preference would be a basic template for building various "monsters", which could also be complicated obstacles. That way we can flavor it as we see fit to our campaign but using guidelines that have been playtested for balance. I imagine it's going to be tiresome if multiple kids keep suffering conditions so that we have to keep spending alternate scenes healing them up using their anchors.