The cron that sends the email is registered as a cron entry under the "Tools" -> "Cron Entries" page. This allows you to pick when the email will be sent. It's defaulted to the first of every month but you could make it as frequently as you want and on whichever days you want.
Your users get the ability to unsubscribe from the email under their "Contact Details" account page. It's a separate option from the admin alerts.
I recommend using Add-on install & upgrade or [#] Install and Upgrade to install this addon.