Fish farms are not really much of a problem in the ionion (other parts of greece yes). There are many many anchorages in the ionion once you have mastered the long lines ashore technique. Make sure you do as it opens up little coves etc where you can be the only boat even in August when all around you is maddening crowds.
Free swinging anchorages are much rarer and usually full. June is a good time as its before the main crowds hit so most town quays usually have a spot for you as well. You will need to get the med mooring technique down pat or become the entertainment for the dock in cross winds

The crowds in ionion are getting worse every year with around 40% more charter boats than 2 years ago now.
Ivory moons itinerary is a good one - south has more than north but its only a day from the lefkas canal to southern corfu so you can do both in 4 weeks easily. If you are over the crowds the gulf of patras is a good option. Some fantastic stops as far east as you care to go though usually around the galaxis bridge the prevailing winds change. We had a surreal day there where we were sailing west DDW under spinnaker while the boat approaching us was also DDW under spinnaker. It lasted till we were about 500 meters apart.
Personally I would let the weather determine the plan especially in June when the summer pattern is still not fully established. If the week you pick up the boat its northerlies go into the inland see south of lefkas. If its calms to westerlies or southerlies then head north to corfu till the pattern changes back to north then its a downwind sail back past lefkas. Too many charterers end up motoring everywhere and sailing little cos they have a limited time and a must do itinerary in their heads regardless of what the weather is doing.