We will be flying from Boston to Athens on May 18, 2018 for 11 days (including travel to & from) (no flights booked yet, so this is our hope). We are a group of 4 cousins - 2 older (50 & 60) and 2 younger (our daughters - 18 & 22). It's been advised by many that we head straight to Santorini when we arrive, which is what we are hoping to do. We would also like to visit another Greek Isle (possibily Naxos?) and then spend the last 2-3 days in Athens. I would love any advice - how long to stay at each island, which islands do we need to see, favorite hotels, favorite restaurants, favorite sights to see. All advice is more than welcome and appreciated!!!! Thank you in advance!

That plan could work! But book your tickets all the way through to Santorini if you can: If you do that, and anything goes wrong with one of the flights, it's up to the airline to get you to your destination. And you might have a greater range of options, too, since you wouldn't be "forcing"a stop in Athens on the way there.

If you haven't already seen it, you might find some useful information in my trip report:
With Gratitude for a Glorious Solo Month in Greece

Be sure to end trip in Athens , you should be in same city as your departing flight , transport to and from islands can hit bumps .

So if you have 11 days , you really only have nine days on the ground ( I don't count travel. Days )

i too would flu to Santorini and work my way to Athens .

I have been to naxos (2) and mykonos (2) and I much prefer Naxos !!!

So your itinerary will look something like this:
Day 1 leave Massachusetts
Day 2 arrive Santorini late afternoon
Day 3,4,5,6,7,8, Santorini and? Naxos Mykonos Paros?
Day 9,10 Athens
Day 11 fly home to Boston
Much better then the Italy/Greece plans and very doable.
You need to buy a guide book and talk with your cousin and daughters and figure out what it is you want to do.
Relax ( beach/pool ) sight see ruins, museums historic sights etc. Then figure out which island has what you want.
Santorini has the caldera sunset views. Not to be missed. But you can also stay on the beach away from the main areas. Will you
rent a car or do you want to take buses or do you want to be able to walk everywhere? How is your health? The caldera side of Santorini
would require you to walk up and down 50 plus stairs at your hotel. Can you do this? Most people like Naxos over Mykonos. I have not been to Naxos
but have been to Mykonos. The beaches in Mykonos are amazing. I own a timeshare in Aruba and the water and sand remind me of Aruba. The island is desert like but great
beaches. My husband and I are in our 60's. We spent 19 days in Greece this past September/October. We relaxed pool/beach and did a lot of sight seeing. We did not rent a car and walked everywhere ( except we took a bus in Santorini from Oia to Firostefani very easy to do) In Athens we stayed at the Hera hotel. A great hotel where we walked everywhere. We stayed at the Clif side suites on Santorini. Enjoy your planning and trip.

Santorini


super paradise beach mykonos


Mykonos another beach