Is there a way I can edit/delete alerts posted by coaches?

No. The athletic director is only able to edit/delete alerts that you have posted.  

To delete an alert, please follow these steps:  

Step 1:Once you are logged into VNN Alerts, click on “Alerts Sent”

Step 2:  Find the Alert you want to delete and click on “Edit”

Step 3:  In the “Edit Expiration” area click on the dropdown and select “Expire Immediately”