I have done a one week charter out of Concarneau. We visited several islands in the region -- Belle Isle, Isle de Groix, Isle de Houat, and the Golfe de Morbihan (entrance just south of Trinité. Benodet is another place to visit - you can motor up the river and see the home of Eric Tabarley with one of his Pen Duick yachts anchored in fornt.
First thing: are you aware of the tides in the region? The tidal range is about 7m, and it more or less has to dominate your planning. For example, most ports have a seuil (threshold) visible on the charts. This is an obstacle placed in the harbor mouth to prevent all the water from running out at low tide. But its existence places a constraint on the hours you can enter (or leave) the harbor. Generally you have about 2 hours around high tide to get in or out. If you miss the window and it blows up a stink, you are stuck on a mooring in the (exposed to swells) outer harbor at Le Palais on Belle Isle. We decided to spend 2 nights in Le Palais so that we could get in a little touring on scooters. With only one night we would have had to skedaddle in the morning or in the dark.
Also be aware that with these large tides you have to think before you tie up to the quai (concrete, not floating). You come in near high tide, tie up to the dock and go for lunch. When you come back your cleats are still attached to the dock and your boat is on the muddy bottom. It really happensto people, so please leave plenty of slack in your dock lines.
Don't plan to cook much on your cruise. Every port, even on the smallest islands, has one or more restaurants which serve delicious shellfish and fish and white wine.
A fun place to spend the night is at anchor in the Golfe de Morbihan ( a good safe spot for your last night -- close to Trinité). You can get a wild ride on the current if you time it right, at the entrance. We measured 2 kts boat speed and 9 kts SOG
In spite of having to pay attention to your planning, it is a beautiful area for cruising. You should enjoy your week.