You can create Events for Alumni and send event notification to Alumni.
Go to Alumni > Events , here click on Add Events button to open Add Event window
Here select event for All Alumni or select for Class - Section then enter Event Title, Event Date (Start - End), Note , if you want to send notification to Alumni then also enter Event Notification Message then check on Email or SMS option and click on Save button.
Added events can also be check on Calendar present at this page.