It’s best to visit Greek islands within the same group. For example, I wouldn’t recommend visiting Corfu and Santorini on the same trip as they’re on opposite sides of the country. Instead, visit islands in the same island group: the Cyclades, the Sporades, the Dodecanese, the Ionian, the Saronic, and the Northeastern Aegean. For one, they’re close to each other. And two, they have frequent ferry connections with each other. For first time visitors to Greece, the Cyclades make the most natural and convenient introduction.
India was also one of the first countries to embrace civil aviation. One of the first Asian airline companies was Air India, which was founded as Tata Airlines in 1932, a division of Tata Sons Ltd. (now Tata Group). The airline was founded by India's leading industrialist, JRD Tata. On October 15, 1932, J. R. D. Tata himself flew a single engined De Havilland Puss Moth carrying air mail (postal mail of Imperial Airways) from Karachi to Bombay via Ahmedabad. The aircraft continued to Madras via Bellary piloted by Royal Air Force pilot Nevill Vintcent. Tata Airlines was also one of the world's first major airlines which began its operations without any support from the Government.
They’re all great choices. Athens (1 to 2 full days) is great for historical sightseeing. Mykonos for beaches and nightlife (2 to 4 days). Crete for historical sightseeing, greek culture and towns, some beaches but spread out (4 to 7 days). Santorini has great sightseeing, tours, and some history (4 to 7 days). If visiting outside of June to September then drop Mykonos and do the other 3 for sure.
Drop-dead gorgeous Fiji is a filmmaker’s dream. Spy its Mamanuca island chain in Cast Away and Survivor; ogle its Yasawa archipelago in the 1980 version of Blue Lagoon. A dizzying amount of natural beauty — from mountains and mangroves to rivers and reefs — swathes Fiji’s 333 islands, and awe-inspiring wildlife (whales, sea turtles, dolphins, parrots) is the icing on the cake. For scenery with a side of luxury and exclusivity, reserve a bure (villa) at one of Fiji’s numerous private-island resorts.
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.