Points on Interest - Bordeaux to Mont St. Michel

Driving time can be considerably longer if it's a Saturday in July or August when people are going to or returning from vacation, especially in Bordeaux, which is a hotspot on the route to/from Spain.

If this is the case, allow an estimated 7 hours to allow for a safety margin.

Leaving Bordeaux at 10:30 a.m., you can stop for lunch in La Rochelle if you manage to avoid the traffic jams.

https://www.holidays-la-rochelle.co.uk/discover/city-strolls/the-towns-of-the-la-rochelle-urban-agglomeration/visiting-la-rochelle-what-to-do-what-to-see

I agree that 7 hours driving time is likely a more realistic driving time. And with the need to allow for lunch, plus gas and bathroom stops en route and dinner before the start of the tour, plus checking into your hotel, I don't think you have time for detours or stops to explore interesting sights or hidden gems. But I hope that the evening tour of MSM is everything you hope it will be.

There are lots of interesting sights and nice places to stop for lunch -- your request is pretty broad.

Regarding lunch: if you really want a "nice" place chances are you'll need a reservation. So, look closely at your departure time, figure when you want to eat lunch (it better be before 13h30 or 14h, or you'll likely be out of luck) and make a reservation ahead of time. If you're not really interested in a "nice" place, you'll have more flexibility. And of course, there's always that world-famous restaurant with the golden arches that is packed with French families and their kids on weekends at lunch. Gives you a chance to have a lunch as many French do.

Regarding interesting sights: how long are you willing to commit? 30 minutes? 2 hours? 4 hours? The answer weighs heavily on what might be recommended.

And regarding driving times: it's true that Google Maps often is optimistic on travel times. It's even more optimistic (that is, inaccurate) when dealing with rural roads in France. Once you're off the autoroute and major national highways, you can be dealing with narrow, winding roads with frequent blind curves and many instances where the rule of priorité à droit (yield to vehicles coming from the right) prevails. Each such intersection requires a prudent driver to slow w-a-y down upon encountering the intersection to confirm no traffic is entering from the right, before resuming a safe speed for the road. The problem with Google Maps is it looks at a route from point A to point B, notes the speed limit, and calculates how long it should take a car to travel that route, accounting for possible congestion in towns. It doesn't really account for the fact that there are numerous blind curves on the route that would require a driver to be suicidal to drive as fast as the speed limit, nor does it account for the multiple slowing episodes imposed by priorité à droit. If your driving route is all on major highways, Google Maps may be off by only 10 percent or so. If it involves small, winding départemental roads, it could be off by 30 percent.