Of the above groups the Dodecanese probably constitute the best opportunity to mix islands between groups. You could, for example, take the Blue Star Ferries and map an island-hopping route that essentially heads in the same direction. In this way you could take in some of the Cyclades – Syros, Mykonos, Patmos, Naxos and some of the Dodecanese – Patmos, Leros, Kos, Chalki, and Rhodes – without any backtracking. Hellenic Seaways is another major ferry company whose routes you may want to explore.
A second financial issue is that of hedging oil and fuel purchases, which are usually second only to labor in its relative cost to the company. However, with the current high fuel prices it has become the largest cost to an airline. Legacy airlines, compared with new entrants, have been hit harder by rising fuel prices partly due to the running of older, less fuel efficient aircraft. While hedging instruments can be expensive, they can easily pay for themselves many times over in periods of increasing fuel costs, such as in the 2000–2005 period.
Airlines follow a corporate structure where each broad area of operations (such as maintenance, flight operations (including flight safety), and passenger service) is supervised by a vice president. Larger airlines often appoint vice presidents to oversee each of the airline's hubs as well. Airlines employ lawyers to deal with regulatory procedures and other administrative tasks.
Be cautious with Santorini and kids. Some hotels don’t do kids (check carefully) and not all hotels are suitable for kids along the caldera lip. Many steps, confined spaces and other guests who don’t actually want to hear kids … Here’s an idea – look for a child-friendly hotel (perhaps on the beach at Perissá) and base yourself where the kids will like it and then take them to the caldera scene. There are a couple of child-friendly hotels on the Caldera, but they get booked very early in the year.
Transport between them can be patchy, but a new service linking Zakynthos with Corfu which started this year now brings all the islands (bar Kythira) together. Zakynthos is otherwise linked to Kefallonia with an old-style open deck ‘slipper’ ferry; Kefallonia includes Ithaki on its local small ferry route to Nydri on Lefkada. There is no link (except for the new service) from Lefkada to Paxi/Corfu. Corfu has links to Paxi and its little know satellite islands just to the north. Kythira has an airport with flights to Athens and ferries to Crete (Kissamos) and the Peloponnese (Gythio, Kalamata, and Neapoli).
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.
Since airline reservation requests are often made by city-pair (such as "show me flights from Chicago to Düsseldorf"), an airline that can codeshare with another airline for a variety of routes might be able to be listed as indeed offering a Chicago–Düsseldorf flight. The passenger is advised however, that airline no. 1 operates the flight from say Chicago to Amsterdam, and airline no. 2 operates the continuing flight (on a different airplane, sometimes from another terminal) to Düsseldorf. Thus the primary rationale for code sharing is to expand one's service offerings in city-pair terms to increase sales.