automatic iTunes backup over WiFi?

I would like my kids' phones to automatically backup to iTunes on my computer over WiFi. "Automatically back up to this computer" is checked. "Sync with this computer over WiFi" and "Automatically sync when this iPhone is connected" are checked. Yet there are no automatic backups occurring despite the fact that phones and computer are plugged in and on the same WiFi network every night. Does "connected" only mean connected with a cable? If so what is the point of being able to check "automatically back up to this computer"? What am I missing, is there a setting on the phone that needs to be dealt with?

Any help appreciated.