Glad to hear you're saving Crete as a future treat ... it will enable you to get the most from the destinations you DO have. And Stanbr is very experienced on getting the most from your visit to the Peloponnese area. A few cautionary observations:
• You say 3 nights in Nafplio -- but from experience, that's not 3 days. Lets do the Math: even with 1st Naxos-ATH flight, u arr 11:30, won't be on road til 12;30 ( then there's lunch -- 30 mins minimum). Nonstop to Nafplio = 2.5+ hours = 4 pm by Hotel check-in... and that's with NO stops . On Day 3, you'll want to return car by noonish at Airport? This means TWO days in Nafplio/area, plus a smidge on either side. Some choices to make:
• Optional Outbound stops (1) Corinth Canal -- 30 mins (just hop off main highway @ Isthmus, see & photo, hop back on )... (2) Ancient Corinth/Acrocorinth -- at least 2+ hrs (3) Ancient Nemea - terrif Stadium! 1 hr ... if u do all four, your hotel check-in may be after 6pm and you'll be exhausted.
• Optional sights in/around Nafplio -- (1) Old Town = Acrocorinth tower/walls & high park, sealevel walk around point, town stairstep lanes & ancient bldgs, small but superb arch. museum, top-ranked costume/design museum, (2) Palamidi - huge "rock" fortress, aerial-height views (3) Mycenae - at least 3 hrs, incl drive (4) Tiryns (just outside town) (5) Epidaurus (drive & return) ... (6) a restorative swim, either at Town Beach/Arvanita, Tolo Beach or Assine/Kastraki ... Jampacked list, leaving little time to relax & enjoy seafront sunsets, relaxed walks thru flower-garlanded lanes. My thoughts based on successful trips with newcomers:
• AFTERNOON DAY 1 - Leave Airport by 1 pm... Choose Corinth OR Nemea ... (if Nemea, u can do the Corinth Canal quik-stop) - Nafplio hotel by 4 pm, late-day stroll Old Town, seafront sunset
• DAY 2 - AM: Old Town/Arch Museum/AcroNafplia... AFT: Palamidi (drive up back way, not climb 999 steps), then a beach?
• DAY 3 - Mycenae by 9 AM! to beat Bus crowds... Or? Design museum. AFT - If still in ruins mood, drive to Tiryns or Epidaurus... On way home stop for swim (I love tiny Assine cove w 1 taverna, NO crowds)
• AM Day 4 -- IF u didn't see Epidaurus or Canal before, get early start, drive EAST to ruins (mainly the theatre), then up COAST road to Isthmus, then hop off for Canal-view, then back on big highway to airport.
I know this sounds like an accountant's stop-watch agenda, not fun... but it's actually the opposite. We found that by planning ahead for realistic timing & choices, (we skipped Mycenae & Acrocorinth, but did all the rest) we allowed plenty of time for a lot of relaxed fun... including a stop at a wine-bottling place right on Main st. of Nemea VIllage near the ruins, several early june swims and 3 swell cafe sunsets. I hope the same for you!