Hey! So the game doesn't really go into anything gore or ultra weird. A lot is kind of left up in the air for the GM to decide how much "horror" they want to include in their final mix. The game generally assumes that characters will fight demons and other weird creatures using guns and magical abilities, but even this you could tweak and say that demons can't be fought since you have to be more clever than them and simply ignore the (relatively short) combat rules.
So my TLDR would be, it's 100% playable with a 10yo but you may have to tweak a knob or two depending on how you want to deal with "violence" in general.