Suggestions for use for date reminders for our team on reports?

Hello, I want to figure out what i should use/make so that my team is aware of report due dates ahead of time by 2 weeks, then 1 week, then 3 days, then day before due date.

Whatever the solution is, once i set it up it'd have to be simple for the office admin to add those dates.. or maybe i can do that for her. With Microsoft there are so many options so I thought i would seek some advice.