We are three retired senior citizens in good health, (seasoned travelers) along with our son who will be driving. Very interested in history as husband has an ancient history degree. Will arrive 9/30 from US.. Will depart 10/9. Planning on 2 full days in Athens then driving to someplace like Itea on 10/3. Will remain there until 10/5 and traveling to someplace like Nafplio. Returning to Athens on 10/8 to fly out the next day. We are curious if we have picked good bases for our stay to drive to the different historical sites. a We plan on visiting the Acropolis, Delphi, Thermopylae, Osioss Loukois, Marathon, Mycenae. Any input would be appreciated.

The monastery of Saint Lukas can easily be visited along your drive from Athens to Delphi.
Plan enough time for Nauplia and surroundinngs, there are many places to visit:
Mycenae, Akrokorinthos, Thyrins, Epidauros........
2 days ar not enough for Athens/Attika if you are really interested in ancient and medeval History.
There is not only Akropolis and it's museum, but also Thission/Roman Agora, National Museum, Byzantine Museum, Benaki Museum, Cycladic Museum, Mitroupolis, Kapnikarea, Kaiseriani, Daphni, the temple of Cape Sounion.........
I would rather skip the Thermopyles and Marathon where is not so much to see. 1 full day is enough for Delphi.
Proceed from Nauplia to the South and visit the ruins of the medieval city of Mystras or go even up to the cruisader fortress of Monemvassia..

Indeed, consider keeping it more compact, with the limited time you have. Skip Thermopylae and Marathon. Doubt if you can add Mystras, worthy though it is, nor Monemvasia.

On the route to Nafplio you can visit ancient Corinth, Acrocorinth and the unmissable ancient games site of Nemea.

Agree with Neckervd about Tyre, Epidauros and more time in Athens if you can.

Any special reason for Itea?

I would concentrate on the Peloponnese Peninsula if your hubby likes history as it's loaded with history from Myceanean to Athens Classic Age, a hotbed for Greece's war for independence from the Ottoman Empire and right to now.

I spent 13 days in the Peloponnese this past October split between 3 towns and could have spent more time as there is so much to see, do and experience.

Nafplio is a great base to explore nearby world class archeological/history sites then you could stay in the Mani for a even wilder experience as it's spectacular scenery is awesome.

The best website for Nafplio is:
https://www.visitnafplio.com/

The best guide book for the Peloponnese is the Cadogan Guide. while last published in 2008 it's still relevant and has more info than any other guidebook.

You can check out my photos of my trip here (click on the first photo to open it and get caption by hovering mouse of it, not all photos have captions.

https://photos.app.goo.gl/2RwHoj4NAxBD7VcZA


The Peloponnese is an overlook part of the Greece where you have more options to experience Greece than any island which obviously have their own special character.

THErmopolyae and Marathon are major checkpoints in Ancient history, but almost nothing t osee today ... Thermopolyae terrailn has changed so radicallyl that it is iimpossible to understand the circumstances of the famous "last stand" ... and Marathon is really just noted with a marker. Save your time for the PELoponnese landmarks ... especiailly the overlooked gems such as ANCIENT NEMEA -- right off the highway!!! and beautifully excavated Sacred Games Site, with stadium where the Revived Nemean Games now attracts thousands.. also Tiryns -- another huge Iliad-era ruin like Mycenae but unrestored, and NO crowds or bus tours.. and again, right off the road, 10 minutes outside of Nafplio.

Add a few more days to your visit so you don’t shortchange Athens.

Can you add more days to your vacation? You really don't have a lot of time in Greece to do everything you want to do. I don't know anything about Thermopy;ae, Osioss Loukois or Marathon so I can't comment on whether or not these locations are worth visiting. But it seems to me that you will be doing a lot of driving around and not spending a lot of time at these destinations/sites. I think it's better to eliminate some places and spend more time at other places so you can fully appreciate what you are seeing. You only have 9 nights.

We visited Greece last May and we visited two of the places on your list: Nafplio on the Peloponnese Peninsula and Athens, (along with Santorini and Naxos).

Nafplio is an awesome base, not only for its beauty but also for the numerous archaeological sites that are nearby. And awesome sunsets! We spent 5 nights in Nafplio. We visited Mycenae, Epidauros, and Mystras. If you spend enough time in Nafplio, you can visit Mystras. It's just under a 2-hour drive one way, and well worth it. Mystras is my favorite of the ruins that we visited. I would re-visit in a heartbeat! We didn't want to spend all of time visiting only ruins; we spent one day sightseeing in Nafplio and followed the Michelin Green guide walking tour. Visited some small churches, and the castle at the top, and had drinks and lunch/snacks at the cafes/restaurants on the water. After we visited Epidauros in the morning, we drove down the Argolid Peninsula where we found a beach and swam a bit, and then had dinner in the fishing village of Ermioni. You might be interested in something like this, or you might prefer visiting the many other ruins that the other posters recommend, and that we, unfortunately, did not have time for.

And I agree with the posters who recommend more time in Athens, especially since your husband is an ancient history buff.

What time do you arrive in Athens? Nafplio is a 2-hour drive from the Athens Airport. Do you think your son would be able to drive 2 hours after an overnight flight? It is very easy driving from Athens to Nafplio. If so, you could drive straight to Nafplio and visit Athens at the end of your trip. If not, then stay at a hotel at the airport instead of going all the way in to Athens center. it's about an hour drive via taxi.

I visited Delphi many, many years ago. While it is worth visiting, it will take almost 4 hours (I think) to drive from Delphi to Nafplio. Only you can decide if that's worth it to you. So a possible itinerary could be:
Delphi - 1 night
Nafplio - 4 or 5 nights
Athens - 3 or 4 nights

If you wish, you can click on my name to read my trip report (with photos) from last May. You can skip Santorini and Naxos and go straight to Nafplio. Athens follows Nafplio.