They are “his children” but they are not children, if you can make that distinction. In any event, he’s implying they are young and innocent and not involved, but none of that is true.
The problem is the English language doesn't have a word that works as well as "children" when talking about your adult sons and daughters. The technical best might be "offspring", but it has that same weird clinical sound as referring to people as "males" or "females". It'd be like trying to use "humans" as the inclusive replacement for "ladies and gentlemen." (That said, "humans" has a certain comedy value in its use.)