TommyK means well, but is writing as someone who's been to Greece a number of times, and intends to go there many more times. However, I would never tell a first-timer not to go to Santorini -- because it is the Big It on every calendar, website, poster, YouTUbe amateur video etc etc. It is the beginner's must-see. I and maybe TommyK were lucky enough to go a few years back before it became such a Disneyland/Times Square/Cruise Carnival ... but the Caldera View is still there, and Joyce is going in late October, and will be spared the mob scene. She has sensibly rationed the isle to 2 nights... and that's fine. As far as Naxos, my beloved Naxos ... I'd rather have her save it for trip #2 than rush in and out. Both Athens and Nafplio will be very lively & stimulating in October ... and she'll be able to compare the Santorini sunsets with those viewed from Nafplio's UNcrowded & comfy (cushioned wicker chairs) seafront canopied cafes (Nafplio wins!). She'll have time to explore the byways of Old TOwn and the countryside... and with a car, perhaps a wine festival near Ancient Nemea -- its the heart of red-wine heaven! Vineyards galore. Joyce, I hope you intensely study the wonderful NONcommercial Nafplio website - http://www.visitnafplio.com/ Open EVERY link, the one on local walks is great, especially the walk @ sealevel around "the point".
To visualize your driving itinerary from ATH airport, try this map (cllick & it gets huuuuge -- navigate around using side-slides). http://euro-map.com/karty-grecii/peloponnes/podrobnaya-turisticheskaya-karta-peloponnesa.jpg ... it shows that you are on a modern divided Intercity highway all the way from airport, avoiding All of Athens, to beyond the Corinth Canal. A little farther on is the quick-stop for ANcient Nemea -- and nearby are vineyards. Many great sites are 5-15 miles from Nafplio itself ... and you can plan it to avoid backtracking ... on your last day, check out early and drive EAST to Ancient Epidaurus, then keep on -- drive up the SEA road to the Corinth Canal area, to stop & see that before jumping onto the biggie highway. It's fun & easy, have done it numerous times with newcomers --- just remember before your trip to stop into an AAA office to get Intl. Driving Permit (takes 20 minutes).
Here are 2 items u may not have seen on your internet research, both from the Masterful forum-contributor, "Stanbr" -- his fine album of Nafplio photos http://www.flickr.com/photos/stanbr54/sets/72157632094108982/ -- his terrific tips on Santorini (1) stress-free sunset-viewing and (2) best place for winetasting on Santorini (a museum NOT a Vineyard) - https://www.tripadvisor.com/ShowTopic-g189433-i245-k13746762-Santorini_3_days-Santorini_Cyclades_South_Aegean.html
BTW, when you begin to think about Athens, and where to stay, I may as well chime in with my favorite location, which is near the Acropolis, toward the South side, near the long pedestrianized promenade that runs all along that side of the Acropolis/agora Precinct. Very Green, lots of trees, small lanes without traffic ... lively but not noisy, right near the Acropolis Museum & So. entrance to the ruins. Hotels to consider include Herodion, Phillipos, Airotel Parthenon, Hotel Hera -- or, if you're a careful budgeteer like me, my secret bargain gem, Hotel Phaedra (3 floors, 24? rooms), no fancy lobby but balconies w either Acropolis or Parthenon view, and wonderful roof terrace open 24/7 to all. Have fun planning; I hope this Covid thing is long past by the time you embark!