If you are looking for an area to sail without the traffic, the Northern Aegean would be perfect. I have spent many months sailing this and the Ionian
, and if it is secluded you want, the Northern Aegean will supply. I personally found the Ionian
fine if you like to stay within sight of many other boats, and don't mind squeezing into may harbours (early too if you want a space). June maybe won't be as bad as a month later however. That said it is bustling, has pleanty of everything you could need ashore, and is generally very gentle (sometimes too gentle) sailing.
Through the canal and over to Chalkidiki however provides relatively sheltered sailing (between the 3 peninsulas) but still some good winds to be had, many days of never seeing another boat at all, beautiful places to stop, and Mount Athos etc as the back drop. It is also devoid of tourists in many towns but loved by the greeks.
I will probably be around both areas at about the same time again next year so good luck with your sail, and please contact me if you need any advice on either areas.