Forget that idea of daytrip from Tolo... that's only in high season. . In making plans, remember that many sites & museums will be on winter hours, closing at 3 pm. Exceptions of course are Acropolis, Nat Arch museum (tho it may close @5). for biggies around Nafplio - Epidaurus/Mycenae, best to check by phone when arrive in Greece, or have hotel phone.
Based on many many trips to greece with newcomers. I agree w others about doing Nafplio & area, THEN Athens, plus a day trip to Aegina during Athens stay. For Nafplio/area, rent car at airport, most efficient way for you: before leaving USA, get International Driving permit from AAA office (takes 20 mins, costs $25); mandatery for rental. Scenario & itinerary:
• BOOK a flight that's nonstop from N. AMerica -- there are 4: Air Canada, Delta, American. U.A.E, from Newark. All leave US/Canada late aft/early evening, & arrive from 9 -10:30 in AM. Costs more than a change in europe but you know the old adage: when you don't have time, you must spend money. If you don't do this, you waste most of arrival day.
• BOOK car in advance for pickup at airport (athenscarrental is VERY highly rec & good rates). Don't need biggie, or high-power , u are not doing hills. Route to Peloponnese/Nafplio is on Greece's most modern, divided highway for 2/3 of distance, then on lo-traffic local road. This map http://euro-map.com/karty-grecii/peloponnes/podrobnaya-turisticheskaya-karta-peloponnesa.jpg (click to enlarge) shows entire route, bypassing athens.
• OUTBOUND (if u can start by noon or before) - over Corinth canal, 15 miles on, Exit RH for ANCIENT NEMEA (Sacred games site) -- olympic runner-up, stadium, the works! open til 3. In heart of red-wine country! Stop in village of Nemea at Wine-bottling plant for tastings! Then onward to Nafpllio to explore Old Town enjoy sunset at harbor (cafes have clear wind-break sides at seafront). Day #2 - Nafplio Museum (small, superb) great overview of ancient civ in area) then Drive to Mycenae, Tiryns, whatever u ca cover by 3 pm. #3 - Palamidi (you can drive up back road, unless ou WANT to climb 999 steps), rest of area.
• INBOUND - Day #4 - in AM, drive EAST to Epidaurus, then up the coastal road to Corinth area; exit at Isthmus to see/photo Canal, have lunch, then onward to airport. Turn in car and take taxi or X95 bus to central athens & your hotel ..
• DAY 5 - 9 - All of Athens glorious msueums, landmarks etc. When weather is forecast for a nice day, go to Aegina. Get GREEN LINE metro (beware of pickpockets to Pireaus.
• ISLAND OUTING - Get a CONVENTIONAL ferry if possible, not hydrofoil (check ferry skeds before); only the conv. ferries allow you to sit on deck & enjoy the seascape... huge freighters, cruise ships, yachts, small sloops, even a dolphin if u are lucky. on Aegina, do a car rental or take a bus or taxi to Temple of Aphaia @ mid-island, then walk downhill to seaside village for lunch. (Get card from a taxi to phone if u want a pick-up). Sunset bev at harborside before return to Athens.
If u want further info, do some research (you guys are academia after all) & come back with specific queries, & we'll be happy to help.