Turning off alerts on a shared iCal calendar

I share a calendar on iCal with members of my family. We are all operating on Yosemite OX 10.10.2. Whenever I put a new appointment, change an appoint or even just consult an existing appointment, all of my family members receive alerts. This is driving everyone completely mad. When my husband or my kids put a new appointment in, it just shows up in the calendar Inbox. What do I need to change to ensure that new appointments will not be notified by alerts and emails but just appear in the Inbox?