The best location: Koukaki, 10 minutes from Acropolis, hip area with great food and bars, and very safe. We spent most of our nights hanging out around our neighborhood, just trying to imagine what being a local would be like.
The apartment itself is amazing -- all the space and amenities that TWO small families needed (air con, washer, dryer, full kitchen). Dark blinds to help everyone sleep at night. Towels, toiletries and tablesettings for us to feel 100% at home.
They arranged transportation to/from the airport/port, and had great suggestions of what to do.
100% recommended if you have a small family, 2 families or even if you're just a couple of single people looking to really immerse yourself into Athens life.