Hi we will be in the area for about 4 days trying to figure out best area to stay and what to see and do please.
We were there last year for four days. We stayed in Auray and went to Vannes, Carnac (monoliths) and Quiberon for a day each. We had a rental car and loved the area. Auray was a beautiful small town with a attractive walk from up town to downtown to a harbor area. There is plenty to see and do within an hour drive. I found a lot of good information on line.
I really liked Vannes as a base. There is a very large medieval center including ramparts that is a great area for restaurants. There is also a marina right next to it. I'd say anything walking distance from the center would be really nice.
My favorite sight was Cairn Gavrinis. You have to take a ferry tour from Larmor-Baden. The tours are limited. I'm not sure about reservations. I went late morning (mid September) and bought tickets for the afternoon, then had lunch while I waited.
Auray was like a smaller version of Vannes. Very pretty and nice old center in a much smaller town.