Taking my 23 year old daughter on the Greece tour in May and looking for recommendations for 5 days after the tour. We are huge history/museum/cultural experience people (she is taking a classics course in University) and while I love the beach I don't love Mediterranean beaches. I am not crazy about hikes. I am considering flying to Chana Crete for two days then going to Herkalion to see Knossos for 2 days then taking a flight there back to Athens to back to Canada (our flight leaves late in afternoon so could take an am flight from crete). Otherwise a quiet stay in one spot kind of small city somewhere near Athens to just chill? Minimizing travel days is a good thing for us and not crazy about renting a car.
A large percentage of people on the forum don't do the tours and aren't familiar with what a particular tour covers.
Here's the tour page:
https://www.ricksteves.com/tours/greece-turkey/greece
It's a lovely tour. Your follow up sounds good, or spend the entire time in Crete, its large. I imagine your daughter might have good ideas if she's studying Classics. Our guide was from Thessaloniki and she used to talk about how overlooked that city was, so you might want to look into that instead. It would keep you in one spot for those days.
It's recommended to be in Athens the day before your oversea flight, unless your flights are one ticket. There could be strikes or bad weather. May 2024 our flight from Rhodes to Athens was cancelled due to wind. We had to fly with the airline the following day, but too late to make the connection. Our trip insurance refunded half of our RT ticket (the home portion) and the missed overnight at the airport hotel.