I have a nice trip in Celestyal Crystal to discover Greek Islands.The ship has a few years but is very well preserved. The food is excellent and the staff is very friendly.
The places I visit are very nice and I feel it is a good way to met some Greek islands.
I am not sure to recommend several excursions but the tour of Ephesus is highly recommended. You can visit the other places on your own perfectly.
The cabin is small but there is enough place to dress, to sleep and whatever.
Mykonos is a plce of full tourists. There are beautiful places to take a drink and anjoy the sunset. I have only several hours to visit the Island but I feel it was enough time to take a look.
I was on the ship.
Santorini has two important cities. The time you have to visit the island is very tight , so you have to choose between Fira or Oia, the second one is the most photographed. Both are very nice.