I don't understand why you are saying that or what that has to do with the conversation. Please imagine a schoolteacher going into a classroom on the first day of school and saying with a straight face to students "I am going to show you a video on how to cut off your leg" or something like that and then not explaining that it's a joke. My original point is not if any given child is competent enough to see the joke or not, but that it could be misinterpreted.