Itinerary help - 10 days, Thessaloniki, Rhodes, and Crete

You've chosen locations that are in completely different areas. It's not like Naxos and Santorini, which are a two-hour ferry ride away.
Your only option will be to take flights if they're available in May 2026.

And the more flights you take, the more days you'll spend on travel logistics instead of vacationing.
So, for what you want to do, you can deduct three days spent traveling. This leaves you with at most seven days of vacation/sightseeing.

In 10 days, you wouldn't have enough time to visit only Crete.

I would skip Crete and keep only Thessaloniki and Rhodes.

Take a connecting flight to Rhodes upon arrival at Athens Airport..

Then a flight from Rhodes to Thessaloniki.

Then a flight from Thessaloniki to Athens.

(There should be direct flights in May, but this remains to be confirmed.)

We were in Rhodes this year in May. I didn't like it at all, but it didn't matter because we stayed only 4 days and it was just a starting point for visiing some the Dodecanese Islands.
In Rhodes, don't expect to see landscapes like those in the Cyclades. All the tourist spots in Rhodes, overrun with tourists and cruise ship passengers, are hell for me. Luckily, with a car, you can see some great, lesser-known places.

We were also in Thessaloniki last year; we stayed there for four full days, which is a good amount of time to see the city.

From Thessaloniki, we flew to the island of Limnos, which I recommend to those who want to see unspoiled places.

https://photos.app.goo.gl/m7hTLLzMavChQmcr7

Thank you so much for this information! Now I can really get to planning our trip!