Is there a specific word for adult offspring? If all of your "children" are now in their adulthood, is there a specific word to refer to them?
The point is that the word child(ren) has more than one meaning, or implied use. Consider the following sentence:
'My children (aged 36 and 32) constantly complain that I treat them as children'. That should illustrate what I mean.
And I have no doubt that these and other meanings will be confirmed by the OED.