Okay, so suppose we wanted to draw a map of where Tiana is at 10 am on a Wednesday. We could draw the school, because we know exactly where that is, and we could draw this classroom inside the school. But how do we show where Tiana is? Is she always in exactly the same place at that time? No.... but we know where she is most likely to be: in this classroom, in science class, in her seat. But she sometimes changes seats, or gets up and moves to a different part of the classroom. And once in a while, she leaves the room to get a drink or go to the office or the bathroom. So she might not be in the classroom at all. And some days, she doesn't come to school at all, like when she has a doctor's appointment. She's probably close to the school, since she lives nearby. And once in a blue moon, she isn't in school and has to travel farther away, to visit a family member, maybe, in another borough or even another state or maybe DR! How can we make one map that shows all these things about where she might be? Well, suppose we shaded the area around her seat. We could shade it in really dark where she is most likely to be, and shade it in lighter and lighter in places where she is less likely to be. This is kind of like the electron cloud diagram - the darker areas tell you that the electrons are more likely to be there, although we don't know that for absolutely certain, and the lighter areas are places where electrons could be, but more rarely. It's not like there's a real fuzzy blue cloud around the nucleus - think of it as a map.
This is the analogy I used with my sixth graders - what do you think? Does it work? Could it be improved?