dkremer,
Just fyi, Brittany is a large area. Two nights means about 1 1/2 days (first day is a morning drive from Bayeux). Where in Brittany are you planning to stay? If Dinan, for instance, you will have a half day, one night, full day, second night, then leave for the Loire Vally the next day. What do you want to see in Brittany? Be sure to allow for enough time to drive around there if, for instance, you want to go to Quimper or Carnac. We spent about four hours en route from Carnac to Saumur, but we traveled on the small roads.
When you leave Brittany, plan on a minimum of 3 hours, depending on where you are leaving from and where you are staying and which type of roads you take (autoroute or not?). It may take up to five hours. Be sure to factor in transfer times to get the most out of your visit. You will be going to one of my favorite parts of France! Brittany is almost like a country unto itself (in a very good way!). I hope you can get the most out of this "land's end" (Finisterre) of France. It does present a majestic face to the mighty Atlantic, and that informs the personality of the Breton populace.
Enjoy your trip and amusez-pvous bien!