Congress passed the Air Transportation Safety and System Stabilization Act (P.L. 107-42) in response to a severe liquidity crisis facing the already-troubled airline industry in the aftermath of the September 11th terrorist attacks. Through the ATSB Congress sought to provide cash infusions to carriers for both the cost of the four-day federal shutdown of the airlines and the incremental losses incurred through December 31, 2001, as a result of the terrorist attacks. This resulted in the first government bailout of the 21st century. Between 2000 and 2005 US airlines lost $30 billion with wage cuts of over $15 billion and 100,000 employees laid off.
Considering your interests (great food, hiking, beaches, nightlife unimportant) then Naxos should definitely be your other island. (And Naxos has many daily ferry connections with both Santorini and Athens.) Also, Athens needs at least one full day to explore so you should drop any thoughts about Delphi or Nafplio. Also, I would look into flights from Athens to Santorini on your night of arrival. If you could get to Santorini that night (and move your day in Athens to the end of your trip) you’d almost gain an entire day and could spend two nights on Naxos.
Less than two hours from Athens, Hydra fills up with chic Greeks at weekends. . They come to disconnect and slow down, but also to see and be seen. Wily cats and weary donkeys patrol the back alleys, but all the action happens along the waterfront. Oh look! There's Olivia Palermo at The Pirate Bar and Chloë Sevigny shaking her tail feather at Hydronetta beach bar. Who cares if there are barely any beaches? You can always find a slab of sun-baked rock from which to leap rock from which to dive into the clearest water in the world.
Where to stay in Crete: A 300-year-old hamlet surrounded by olive groves, Kapsaliana Village Hotel exudes peaceful authenticity. On a sandy bay just beyond Chania, Ammos Hotel smartly combines Scandi chic with a child-friendly vibe. Blue Palace Resort & Spa beats the (stiff) competition in Elounda with its spiral stone Isola Beach Club, thalassotherapy spa, and boat trips to Spinalonga island, a national monument just across Mirabello Bay.