without providing delegation to any user no one will be able to Access your mailfile calendar (except Notes Admins) . In that case you can share your ID file & password to the user who need access to your calendar .
Note : if you provide your ID file & Password , user will be access your calendar as well as Mails ..
If you go into Preferences and then to Calendars and To Do’s you have the option to give access to your calendar and to do’s without giving access to your mail file. Pick the users you want to give access