I agree the choices aren't ideal but I think "likes children", "dislikes children" and "doesn't want children" all match a search for "Doesn't have children"

Particularly not ideal in as much as only 'likes' and 'dislikes' are mutually exclusive among those options. But I suggest that anyone who puts both 'has children' and 'dislikes children' on their profile is being far too honest for their own good. ;)