I would suggest Peloponnese stint FIRST, and do island upon return toAthens area. Fly from Paris AM March 26, get car at airport. Drive to Nafplio, sights along way. After 3-4 nights there, drive back different route, drop car at airport. Bus to PIRAEUS, ferry to Island (be sure you want Hydra ... do u know it really has no beaches?), then final days in Athens.
PELOPS INFO - This is a GEM - http://www.visitnafplio.com/ - noncommercial website by a Sandinavian expat who lives there... click on EVERY link, where to go, eat, walk etc. Here's a photo album by Nafplio-phile "stanbr" showing highlights of this most beautiful Old Town in Greece http://www.flickr.com/photos/stanbr54/sets/72157632094108982/ - plus nearby sites.
TRANSPORT -- You CAN bus to Nafplio & back, & rent car while there... but do consider driving from airport. It really is THE easiest --just 2 hrs, Greece's most modern multi-lane divided highway 3/4 of way, then on small road thru valley, almost no traffic. No Stress; in 2013 we even did it in a shower, no problemo. You need to stop in local AAA for 20 mins for International Driving Permit. Many of us "vets" use highly reliable great- price agency - http://www.athens-carrental.com/ - order an automatic. A guy meets u @ airport dor, escorts you to car outside & tells where to return it. Last June we had new Hyndai (like a honda accord) automatic, drove like a dream. See this fab online map to plan route - http://tinyurl.com/zekuft9 - click & it gets huuuge, use sideslides to navigate. It shows that intercity highway bypasses Athens entirely, skirts the northern fringe you stay on that road til way after Corinth Canal. Use it to assess my advice for your itinerary:
Day 1 • About 15 mi past Corinth Canal, exit RIGHT (N-W) for ANCIENT NEMEA, just about 3 miles in... A real treat! Ancient stadium, where yr daughter can race from starting-blocks 2400 yrs old! Hero's tunnel.. plus ruins temple columns, small museum... easy to enjoy in 1 hr. Return & cross (under?) highway, go SOUTH to Nafplio, thru citrus orchards & olive groves. Park car free on wide concrete pier @ seafront. Hotel? Agamemnon.if u can get a room... if not, Omorfo Poli is lovely small boutique just off seafront... In late afternoon, wander town & enjoy sunset at cafes on seafront... best sunsets in Greece IMHO.
Day 2 - Drive up BACK of Palamidi for Photo Ops -- your daughter can walk down the 999 steps, & u can wait for her in cafe at foot of stairs (that's what I do). Take elevator in the Cliff (yes!) up to Acronafplia.. the ramparts... & walk around the peninsula point at sealevel -- stunning photos! Don't miss small & good museum in Nafplio main square... and BTW, since Nafplio is a favorite weekend getaway for chic Athenians, it has tons of nice shops -- I always shop there not Athens.
Day 3 - If u want MYCENAE, go EARLY (dozens of tour busses arrrive about 10 am) ... do Museum first, to understand it .. I'm partial to another Iliad-era Fort just outside Nafplio -- TIRYNS - not "restored", huge boulders, awesome,NO crowds. Ask hotel for day of local market (on nearby street), other events, & walks/activities in visitnafplio website
Day 4 - Check out 9 am & instead of backtracking route, drive EAST across "thumb" of peloponnese to EPIDAURUS. En Route, keep eyes peeled to LH side of road -- for Oldest Bridge in World in Continued Use (Mycenaean, 1800 BC) - great photo Op! http://en.wikipedia.org/wiki/Arkadiko_Bridge. At Epidaurus, acres of rubble, but just spend time in stunning THEATRE! People stand in center, sing to top rows. Afterward, drive up the SEA ROAD... when u get to ISTHMIA, stop & find the Old Bridge over Corinth Canal (great sight; so deep so skinny!). Stop for lunch, then back to aTH. The only key turn in entire trip - turn LEFT for Airport, not right (city traffic!).