I have slightly the same dilema - over the past few years we have had to keep putting the holiday back again and again - from mid two weeks of June now to mid two July weeks, we also did this - this year, and will be doing so again next year.
The prices tend to go uo at the start of July - and again in various places at the beginning of August. So you won't notice much difference there. The real busy time starts around the 3rd Monday in July - that will be your half way point. having said that, due to the limited number of beds on the island - its not really a problem, just an awful lot more day-trippers around for your second week.
Still wonderful - whenever you go, but August best left to the Italians !