Crete, Santorini, and Naxos look quite doable within the 12-day block, but Crete’s beaches are scattered throughout a very LARGE island, Santorini really only has Kamari and Perissá (and some southern coast bays) and Naxos does have nice places to swim. If you choose only to visit those three islands in your relatively short time, you will do well.
Yachts moor in the deep, sheltered harbour of Vathy, or Kioni, a miniature port where you’ll find Spavento, the perfect pier-side café-bar. Go any time of day or night for ice-cream sundaes, excellent cocktails, and a soundtrack to make your heart sing. Ideal for low-key family holidays or retreats, rugged little Ithaca is somewhere you can still disappear.
The Greek islands have beautiful weather in the months just before and after peak season. It’s a great time to see the islands, save money, avoid the crowds, and still have great weather (though not as hot as July and August). If you want to see the super-popular islands of Santorini, Rhodes, Corfu, and Crete without the tourists then this is a great time to visit.