A bit like when we renamed all the master/slave terminology using different phrasing that's frankly more useful a lot of the time, I think it's about time we got rid of this "child" task nonsense. I suggest "subtask". Then we can reword these books into something that no-one can make stupid jokes about any more, like "how to keep your subs in line" and "how to punish your subs when they've misbehaved".