Hi Georgie, Thassos gets my vote too and the ferry over to Thassos from keramoti port is a wonderful start to your holiday, I think though that only Thomsons fly into Kavala airport although I have to say the short [ 8 mins] coach to ferry port then 35 mins on ferry which has a bar serving drinks and snacks then a coach waiting to take you to resort once off the ferry is very well executed by Thomsons, no hassle at all plus the seagulls follow the ferry over to Thassos and if you are lucky then you will get to see the dolphins.
We stayed at ' Golden beach' in Panagia which is a lovely resort, amazing sandy beach, with lots of friendly taverna's serving lovely food in a chilled out place. Thassos is only 90 kilometres all round with very good roads, you can hire a car or motorbike to visit some of the other stunning beaches such as Paradise beach or Marble beach, Thassos town is worth a visit too. The old quaint village of Panagia just above Golden beach resort is worthy of a visit, a lovely old village, you can either walk or catch the frequent bus service, only takes around 15 minutes by bus and there are some lovely local shops there too.
Having said that SS is the only place that we have ever been drawn back too, can't explain it but just love it, next year will be our 3rd visit to SS having previously stayed at nearby Agios Georgios North until we discovered SS.
Good luck with your plans.