I think it is important for you to capture systematically (not via user input) WHO is entering the employee reviews and WHEN they entered it. Its important that the system capture the current wordpress user along with date/time and not rely on the the user themselves telling you. This prevents people from maliciously entering invalid data without a system audit of who performed the action. Since your system allows someone other than the person’s manager to enter reviews on them, I think this is a very important feature.
This should be an easy addition for you to make to your system.