Hi Sarah

Some possible options for this

• Create a forum with a timed forum post in the future and subscribe reviewers to the forum

• Add a course calendar event for a user or group and allow alert message preference or export to users external calendar and they get a reminder from their external calendar

• Create an activity that reviewer role can complete and add an activity completion notification after a set amount of time

• Create a event monitoring rule triggered by an event on the course and reviewers can subscribe to the rule

Regards