In the summer you will have not problems with too strong wind (over force7) and more probably you will have weak to medium winds. normally the wind rises in the afternoon and dies at night. Just perfect
The number of shelters is so high (between the Islands) that only a very bad sailor can have any problem.
I have been there on the last summer, first touring by car ant then by boat (2 weeks). There are so many Islands (+2000), so many nice places that you would take several years to explore half of it
I have charted with Ban-Tours and I have only good things to say about them.
As TejasSailer said charter companies provide you with information and itineraries, that you can follow, or not.
On the Ban Tours site they suggest some itineraries. the information that they will provide you of those itineraries is much bigger than the one they have on the net (PDF with photos and descriptions).
Here you have a basic view (the ones to the South ones are more interesting):