Road trip in France...Rough Itinerary

Bonjour!

Regarding your questions:
1/ You could shorten the Loire to 3 nights and stick with 2 castles, it is enough. It is nice to break the long drive between Brittany and the Dordogne, and the Loire Valley allows to do so (even though it is a slight detour).
2/ Brittany is GREAT in summer, and you could easily spend more than 7 nights in Brittany (but 7 is already good!)
3/ It is interesing to be in Paris on 14th july, especially if you can see the military parade, but most towns and cities have 14th July festivities incl fireworks so do not build your route around that constraint
4/ You should go towards the higher end of the # of days you list for each place, adding even a 6th night in Dordogne if possible, and spend the remaining 2 nights in the middle Loire Valley, for instance in Sancerre. This could let you visit Guédelon castle (fun w/ children), Briare, and the Sancerre area, and it breaks the drive back to Paris from Auvergne. You also need a final night in Paris if that's where you leave from.

In Auvergne, I would recommend Besse as a base. Charming town right next to some key highlights of the region (Puy de Sancy, Cézallier lakes, waterfalls...). VERY French.

@Balso; Thanks for that answer. We will make some search about the places you recommend !

@kerouac2: I,m curious to know about your opinion on Britanny and Normandy and why you think the north/eats is better than them !

South of Loire, you may be interested in with the kids. Just saw it during an episode of International House Hunters of all places.
https://www.la-vallee-des-singes.fr/en/
and something close to there called Futurescope

Adding a few comments.

For Normandy, with 4 nights it makes sense to keep a single base. Etretat and the D-Day beaches are a fair distance apart, so I suggest you stay somewhere in the middle. Close to Honfleur and along the coast west of Honfleur would work, I would just avoid Deauville and Trouville which are much more expensive than neighboring places and full of snobby Parisians (OK, a bit of a cliché... but I stand by it).

After that, Brittany is quite large, so I suggest that you do not drive all the way to Finistère.
A northern base on the coast between St Malo and St Brieuc would be perfect (St Lunaire, St Briac, St Cast le Guildo...). You could then move to a southern base around Carnac / La Trinité sur Mer.

Now that I re-think about it, the Loire is definitely a valid option, but you could consider a more direct route to Dordogne. The Futuroscope outside Poitiers is a good amusement park indeed, and Puy du Fou is also worth a mention with its top-quality historic-themed shows.

Nantes is still on my bucket list and certainly want to visit “Les Machines de l’île”, fun for the kids and parents as well.

Brézé Château in the Loire, this medieval troglodyte château is absolutely fascinating. Your children will love it.
There's also the usual above-ground Renaissance palace with a room prepared for a king's one-night visit. I'm not big on châteaux.

Seek out the other troglodytes in the Anjou end of the Loire. There's a troglodyte farm, now a museum, and more near Douai-la-fontaine. Up until the 20thC, 95% of the Anjou population lived underground. I find the Anjou more interesting than the Touraine.

Auvergne : look up Le-Puy-en-Velay. Bring sweaters as it's in altitude.

Another vote for Northern France and Alsace-Lorraine.

When I started to venture out of Paris, Versailles and Fontainebleau, I focused, first and foremost, on the North, always going there in the summer.

Cities like Amiens, Arras. Lille, Metz, Strasbourg, and small towns/villages in Nord Pas-de-Calais and the Somme area I found curiously interesting and fascinating , eg, starting from Compiegne , Frevent, Doullens, St Pol, Vimy, Bethune, Neuville St. Vaast, Lens, Albert, Beauvais,

Lots of the towns, basically the whole area, were fought over in both wars. The countryside from Arras to the Belgian border is dotted, plastered with British and Commonwealth military cemeteries from WW1. The German WW1 military cemeteries are there too but not as obvious . I've tracked them down too.

If one subscribes to the "backdoors" idea of traveling as regards to France, come to Northern France. Hardly ever any anglophone tourists or visitors; no international tourists. If anglophone, they are British and Canadian.

Hello from Wisconsin,
Normandy. There is no need to stay in a room on the beach. The nearby city of Bayeux would be a solid place to stay. It has a really nice market day and restaurants. There is the cathedral and unlike so much of Normandy, which had been destroyed and rebuilt, Bayeux was captured so quickly that the invasion destruction was minimal. The allies built a ring road around the city so a lot of military traffic even avoided the city center. And it has the Bayeux Tapestry (a Normand invasion going the other way), and good WWII museums.

Brittany is windy, wet, and cold. You are going in July so it will likely only be windy and wet.

As for starting with 7 nights in Paris. Maybe you were able to book a good place because of the seven days. I have found over our many trips that landing and staying a few days in Paris, or Budapest or where ever, and then returning at the end of the trip to the same city, turns out to be a good plan. The first days lets you acclimate, get a grip on where things are located, and how far apart things are. The return trip allows you to do those things in the city that you learned about since you landed.

The Dordogne area. There is a cave in Cabrerets, named Pech Merle. It is a ways fro the Dordogne with the castles but this a great cave with prehistoric paintings.

wayne iNWI

Amiens was the very first city I visited in Northern France when I started to venture out of Paris. Besides the famous cathedral, my main reason was to see where the Somme flowed through Amiens. This was in August 1989 as a day trip from Paris. I didn't know about nearby Fricourt and its German WW1 cemetery at that time.

"...the huge military cemeteries...." How poignantly true !

Two of them really hit me the first time I was there...."Notre Dame de Lorette" / Pas de Calais (the French WW1 ), and the German WW 1 military cemetery nearby, as you slowly go by and read them.

www.cntraveler.com/stories/2013-03-03/gourmet-mushroom-cave-loire-valley-france-vacation/amp

My kids liked this in the Loire. I did too. We did this and Chambord one day. Nice relaxed pace.