My husband son and I are traveling to Greece for 1week in mid June. We are planning on first 3 nights in Athens, including a day trip to Hydra island, next 3 nights in Santorini and final night in Athens before flying back to Chicago. I am wondering whether I should substitute Hydra with Mykonos. So it would be first two nights in Athens, third night in Mykonos, 4th 5th & 6th nights in Santorini and final night in Athens. Please advise which itinerary is better?