Do take special care to go the Athen. The security in general is deteriating these years due to financial difficulties. Though there will be less tourist in September and not so congested but I would prefer to go there at peak season as you will not be the only target. The umemployment rate is as high as 40% for youngsters.
Don't go to Turkey. This country is pretty unstable. If you really wanna go, please concentrate at Istanbu.
Economy is not good these for Europe. So, when you go to travel, really need to pick good timing and location. Personally, I think more tourist, better security.