"Child" just refers to those boards' relationship. For example, Current Talk I and Current Talk IX are child boards and Current Talk is their parent board. Another way to look at it is that Current Talk I and Current Talk IX are sub-boards of Current Talk.
And there's no need to curb your language on any of them. If you try to say something that the forum's system might object to, it will merely be censored once your post has been submitted.