On your Joomla 3.x platform website, you can include several calendar displays as demonstrated on this page. Below is a full month layout and at left is an 'Agenda' layout.
This feature does use a free Google account for the base calendar which can be managed from there to add, edit, and delete events on the calendar. It is recommended that you setup a free Gmail account for your campaign. Give your campaign staff access to this account so they can take care of any updates for you also.
The main purpose of this Gmail account is not so much for a publically available email address, but more for the features Google makes available for your site by having this free account - the calendar being just one of them.
The Google Calendars being used in the displays are linked to in the displays so the visitor can add the events listed to their own calendars.
On the Google Calendar, you can have both public and private calendars. On your website you can also do the same, but that is another topic on Access Control Levels (ACL).
With ACL setup on your site, you can have different levels of what can be viewed by those visiting your site. Levels can include general public, site registered general public, campaign staff, and site administrators.
You can have calendars for the general public and separate calendars for your campaign staff. The latter is a great way to keep your staff coordinated using the on-line Google calendar feature. If your staff has been given access to your Google account, they can edit the events themselves using the link in the calendar displays.