My brother plays in an occasional OSR/Stonehell game I run for my niece and nephew (ages around 9 and 11). I don't tend to adjust the way I run the game for the kids (I'm a little more circumspect in some areas, but overall, not a huge difference).
Last session, my niece used a sleep spell on some berserkers. My brother decided they needed to be despatched to prevent later issues. If my players want to murder helpless foes, I'm not going to sugar coat it so, when my nephew's cleric joined in the slaughter, I mentioned the mace caving in heads. My brother thought that was a bit much. I just shrugged -- he's the one one that encouraged this course of action, if he doesn't want his kids involved in this kind of violence, don't suggest that course of action.
To be clear, I don't usually add that level of detail in this particular game, but if you're going to go all murderhobo, you don't get to ignore what that means.