We will be driving from Dinan to Amboise in May. What would be the best route and what would be a good mid-point for an overnight? Any advice is appreciated.
It's a drive very easily done in a few hours. But if you want another place to explore, you could stop in Angers, on the very edge of the Loire. Bonus, Google maps says that route is toll free.
Here is a recent discussion of a very similar question:
You could stop to see the succession of 11 canal locks around La Petite Magdelaine. I see that there's a small museum there: http://maisonducanal.free.fr/index.html.
Fougères is a pretty village covered in Rick's France book and used by our tours as a lunch stop when driving in the opposite direction.
Have to say didn’t visited it yet but Sainte Suzanne (pretty much halfway between Dinan and Amboise) west of Le Mans is a lovely village in case you prefer a smaller place to overnight.