When you make a change to something on a canvas course there should be a small tick box that says notify users that this content has changed
This will send a ping out to all students enrolled to let them know it has changed.
As for due dates, any students who are registered on your course and assigned to the assignment will have the due date showing in their calendar. If you go to announcements you can set it to send to people who haven;t submitted a piece fo work yet, and that will send a pop up to them.
Hope this helps!