Well, dev_cw, your question about published children helped me discover that the documents, which are private, are not returned by Ditto 2.0.2. I see from the on-line documentation for 2.1.0 that there is now a hidePrivate parameter (
http://ditto.modxcms.com/files/snippet-ditto-php.html#hidePrivate) which would seem to be just the ticket. I will upgrade Ditto and try again.
Thanks for you help, even if indirect.