We just returned from 3 weeks in Greece. We took a cruise to see several Islands and then did the Best of Greece. Just a couple of things to share regarding Athens.
There was an issue at the Acropolis museum in that we entered as a group and did not have an individual ticket like we did for the Acropolis itself. We had our tour and then stayed to eat lunch at the museum (great food). After lunch we were not allowed to go back into the museum. This happened to several others in our tour group that stopped for lunch there. If there were ways to eat there without having a ticket we were unaware. But we were directed to the elevators which went to the exit. Our guide later said this might have been a recent policy change by the museum. So hopefully you get a ticket for future tours or else make sure you see everything first.
Regarding the afternoon is Athens - we were cut loose after the museum. For some reason I thought there might have been more that day so I'm very glad that we had booked re-tour a food tour that took us thru the Place, Monastiriki end the fish market. We also did the Beneki museum on our own pre-tour.
Overall we really enjoyed the 2 week tour and now I have to decide where to go next!