Came here to say pretty much this. Kids aren't stupid but they are not going to have the same things on their mind as dad. Dad's got a million things on his mind, and he's probably meta-observing the entire play session at the same time... he's not going to notice the arm sprite of a zombie in a plant. Now reframe this as a question: what the hell else is a little kid going to pay attention to other than what's in front of them right here, right now? That's part of what forms the beauty of childhood.