Last year travelling in early Oct the slow ferries were still fine but the fast ferries and flights were booked up when we tried to book about a week beforehand. We ended up taking the slow ferry from Santorini back to Athens (about 10 hours). That was a long haul!

We stayed at Katikies in the north of the island which was very beautiful, G-friendly. Small pool and good restaurant (books up early, only 4 tables). Great views and one of the best massages I've had in my life.