The plan is good in my opinion, but you're free to tweak it a little if necessary.
A few tips
Regarding flights: Sign up for the Aegean/Olympic newsletter, the Greek national airline (at the bottom of this page)
https://en.aegeanair.com/
There are regular discount offers on flights; you will be notified by email. For flights in June/July 2026, you can wait until March 2026 (I take advantage of them every time; this year I got a 50% discount on two flights).
Sky Express, the other Greek airline, also has some promotional offers: https://www.skyexpress.gr/en (also at the bottom of the page)
You can find ferry schedules on ferryhopper. Some ferry companies only publish them 2 or 3 months in advance. Don't worry, you'll always have seats available even if you book only a week in advance. Prices and schedules don't change (or hardly change) from year to year.
See an example of a Crete→Santorini route for this coming Sunday:
https://www.ferryhopper.com/en/#/results?itinerary=C00,JTR&dates=20250622
Another example for a Santorini→Amorgos route:
https://www.ferryhopper.com/en/#/results?itinerary=JTR,AMR&dates=20250629
The price difference depends on the type of ferry; Seajets' fast catamarans are always more (too) expensive.
A rental car is always the best option for getting around the islands. You are free to go wherever you want, whenever you want, without depending on bus routes and schedules. You don't have to rent a car for the entire duration of your stay on an island and
I don't think you should worry too much about driving on the right. I don't know the statistics for New Zealand, but about 350,000 Australians come to Greece each year, and I'm guessing quite a few of them rent a car.
Anyway, driving in Greece, even on the islands, isn't particularly difficult. Anyone on this forum can confirm this.
There are plenty of accommodation options, from basic hotel rooms to large luxury villas with private pools.
There are far more options in small, short-term rental properties (studios, apartments, houses) than in traditional hotels. Depending on how you're traveling and what means of transportation you'll have, there are three factors that determine whether a place to stay is the right choice for you:
- Location
- Location
- Location