Set update cron weekly

Since i have my child sites set to make complete backups once a week i would like the feature to set the automatic updates on the dashboard site for child sites to run weekly in stead the max once a day option.I try some things via support but without advanced coding skills i think i ran out of options so offering this as a feature request.I gave this a shot with the wpcrontrol plug in and was able to edit the mainwpcheck for updates cron event to weekly. My dashboard site waited a week to check for updates like hoped for. However it did not actually ran the updates once he checked for it. Daily sync time was set to twelve times a day, all is set to trusted updates but nothing happend. Like it was waiting for the next week te actually start updating. Disabling and re-enabling the daily update frequency set my mainwpcheck for updates cron back to every minute in stead of weekly. So it seems both (checking for updates/updating) are part of one event what makes my goal to check/update my child sites weekly seems impossible?