I am traveling at the end of June. I only have 3-4 days to spend in Greece. I've never been; 49 yr. old traveling with College son. What are the must see/ todo's. Coming from Prague flying into Athens
With so few days just stick close to Athens. Spend a couple of days seeing the sights then take a short ferry ride to Hydra, a very charming island, still with an old-world 'feel' because no cars are allowed
You need a couple days to see the sites in Athens. That leaves a daytrip to Delphi (well worth it) and maybe a daytrip to Hydra.
You're on the right track with the advice above. You won't have time for all of Athens' museums, but most people are happy to see just the top few. See http://www.ricksteves.com/europe/greece for an overview of the sights mentioned, which are also covered in Rick's guidebook.
i am living in Paros island which i am sure is an island that fit for you and your son also. it is one of the islands that combine holidays for all ages and tastes as it offers many things to do like sightseeing, villages, activities, nightlife, good food ofcourse, and easily approached beautiful beaches. Parikia or Naussa are the main villages that i suggest for you to stay so you can enjoy the nightlife there, as the other villages are a bit more quite. the boat traffic from Athens is easy and frequent. it is four hours distance with the normal ferry or you can catch the speed boat as well.
have a best time on your first holidays in Greece!!