My family of five adults will be in France at the beginning of October. After a week in Paris, we'll be driving to Caen in Normandy for a two-day stay. On the way there we are thinking of stopping at Giverny, Rouen, and Honfleur. I'm wondering if this is too ambitious given that one of us is in his 70s with back problems which means that we will need to stop the car for a few moments every hour.
The 3 destinations you've listed (Giverny, Rouen, and Honfleur) are pretty well lined up one with the next. I can't speak for how interesting or beautiful each one is, but the drive is probably realistic. I can relate to the back trouble and the need to stop and stretch every hour -- the latter is actually a good idea for everyone!
During your Normandy stay, do you plan to visit the D-Day beaches west of Caen? If so, I can vouch for the American Cemetery at Colleville-sur-Mer and the monuments on the beach at Vierville-sur-Mer as being very much of interest (and very moving) for anyone with an interest in WWII history. The Hotel Logis du Casino at Vierville-sur-Mer has a lovely glass-walled dining room overlooking the beach and the remains of D-Day battle structures.
When parking at these beaches, watch out for the "buses only" parking lots -- the bus drivers will block you in if you park a car there.
We'll be devoting the next day to the beaches, and I certainly do appreciate your tips on that. The day after that will be the eating and buying day: cheese, cider, calvados, etc. Any suggestions for where to wander for that? We return to Paris that night. Yes, I know it's not enough time but it's all we have!
I have visited all of these Norman destinations. They are all worthwhile, and Rouen is an especially nice pairing with Giverney if one visits the Marmatton museum in Paris beforehand to view the paintings Monet made of the cathedral in Rouen in different lights. (I think some of those paintings may also be in the Orsay.)
However, you are proposing a long day for anyone in any condition. The car portion is only 3 or 4 hours, so stopping for "a few moments" does not add much time, if that is the constraint. It is feasible. But it is a lot, so I would not commend this plan unless everyone has good sightseeing stamina.
Are you planning to do anything when you get to these towns or just drive through and what time are you planning to leave Paris? With zero stops along the way, you will have about five hours of driving time on this one day and that is assuming that there is no traffic. I think the itinerary is too ambitious for one day even without regard to having a member of the group with back problems if you want to do more than drive through the stops and say that you have been there. I'd drop Honfleur.
As others have said,the itinerary is a bit ambitious for one day. We loved Honfleur (stayed there one night).It's not that big and there are some wonderful restaurants. I would drop Rouen. Giverny is always busy and you wouldn't be doing it any justice by just quickly going through it. JMO