We stayed in Mare Civitas for one night before our flight from Chania Airport. It's clean, reasonably equipped apartment with great location, close to the center of Chania, just few steps from beach and taverns.
All apartments have pin-locked keys, so you can check-in and check-out any time, without speaking to single person. This is extremely convenient when you are in a hurry (like we were), it lacks this personal feeling hovewer.
It's safe for kids, both balcony and inside are perfectly good playzones.
One thing to remember is that Mare Civitas 3 is located at third level of a building with no elevator. Can be challenging if you're carrying a lot of baggage.