If you do type www, the browser will take you to the actual address of your secure site, which does not have www.
This is how masked-URL Lookatme sites are to set up as standard:
The only way around the third option failing is to buy two certificates or a wildcard certificate, which is entirely unnecessary and would cost up to a thousand dollars more each year.
Based on empirical evidence, this is an issue that does not have to be addressed at all – we have never had a help desk enquiry from a user typing in https://www/...
All our clients who have bought their own SSL certificate only bought one single-domain certificate. When Lookatme buys certificates for clients we only buy one single-domain certificate.
The best way to promote your URL to your users is like this:
If you wish to make it a link, either add https:// at the front or right-click in Word and add as a hyperlink the full URL which is like this: https://yourdomain.com/.
www is a bit old-school now. Most people do not type www these days.
If you really are addicted to www then, very well, you can tell users to add www and it will be OK, the users will be redirected to the real address anyway.
Never tell users that the address starts with htttps://www.