If you just want one seat I see five days in August with J availability on the PHL-ATH US Airways flight. That's on an A330 with their Envoy suites which I hear is quite nice. For two seats I only see availability on Aug 10 and 11.

Another option is to fly Turkish to Istanbul (IST) and connect to Athens or the islands from there. I see six dates in August with one seat and two dates with two seats on JFK-IST in business class.

I only checked the non-stop flights into that part of Europe from the Northeast that I knew of. If you want to fly farther to connect there are also TK and UA flights to IST from ORD, IAD, and IAH that I know of. Connections in Europe were covered pretty well already, and I'm not as familiar with those.