We are a family of 5 and we have spent 3 days in Thessaloniki at Stef & George's apartment. Our stay was excellent. The flat is very well located and equipped with everything you need. George was also very responsive and helpful to help us get the keys while our arrival was delayed in the night.
One minor thing to improve though: some fixtures were not finalised or needed to be repaired such as a shower hook or two sleeping room locks and the wardrobes are already half-full which leaves little room for your own stuff when you arrive. That said, I very much recommend this apartment for stay in the very nice city of Thessaloniki.