We stayed at the Villa Olivia for 3 nights. We were a family of 7 + 1 infant, and enjoyed it immensely.
Structured and organized in a very clever way, this place easily accommodates 8 people, but can even more if those would sleep on one of the two sofas.
It is very convenient and includes 4 bedrooms, 4 toilets, 3 bathrooms (one has a small Jacuzzi in it), 2 terraces (one has beautiful views to the port, especially at sunset), a kitchen and even in indoor elevator if someone gets tired of stairs.
The place is run by two lovely ladies, Nandia and Anna, who - in addition to being genuinely nice - have been super attentive and responsive, before and during our stay. Possibly the quickest response time I had encountered when travelling.
Two points to consider though - one is the location. It is not in the 'heart' of Athens where all the restaurants and bars are at, but rather in a simple neighborhood, ~20-30 minutes walk from everywhere. We actually liked its quietness and the walks, but it is something to consider, especially since Athens is sometimes rocky. The second is that there are no spices, oil, etc. so if you are planning on cooking - you should take care of that on your own. The kitchen itself is fully equipped however, so no need to worry about that.
Bottom line - HIGHLY recommended!
