First off, i love what you’ve done with the place.
Now, as far as the gesture thing goes, you referred to Greeks using the thumbs up as an abusive gesture. having successfully been a greek myself for the past 38 years, I can guarantee that this is not the case. There is an abusive gesture involving use of the thumb in Greece, but it is slightly more complicated: it involves tucking the thumb inside your closed fist and exposing the tip of the thumb between the index and middle fingers. (That’s a handful!) However, this particular gesture was by no means used all over the country (mostly up North) and it seems to have totally disappeared now. While I remember both my parents admonishing me for using it when I was seven or eight, I don’t recall having seen the gesture used in the past twenty years or more.
Anything other info you need on modern Greek culture (if such a thing exists), just drop us a line.
Cheers!