Must see stops through France

[orridge]

I was going to suggest this.
We will deffo be having a look on our way home.

The Mechanical elephant and the carousel are amazing in Nantes. For something a bit closer Calais now has the Dragon made by the same people as it Nantes in the area the old Aire used to be that they have re-developed.

 

[billym]

Are you crossing into Normady of Calais / similar? If crossing near Calais, I would go to Paris too.

Puy du Fou (2 days)
Futuroscope (2 days) or at the least, arrive in the afternoon for a late afternoon visit and then a full day. The late afternoon tickets are a lot cheaper and the queues are smaller so you can get lots of the key attractions seen without waiting long.
Prehistoric caves in / near Dordogne paintings made by "cave men"
Dunes at Archachon
5 days chilling in one place x 3 at least. It will be hot. Your kids are likely to want to spend time chilling, swimming etc and there is a risk that they will get overwhelmed with so much site seeing. Perhaps first stay on the Britanny coast (but watch for powerful waves), 5 days in Dordogne and 5 days in N Spain beaches (sandy beaches with and generally smaller waves).
Carcassonne

I wouldn't do Oradour-sur-Glane with such young ones. It is emotionally draining and you'll have had quite a lot of "war" at the Normandy beaches; I'd wait until the youngest is 8 or more but others may say different.

Condom is quite chilled - nice options for sampling Armagnac for the adults and a great municipal pool with slides etc. for the kids.

If the weather is very hot, you could have some diversions into the Pyrenees or the Picos to get some altitude, cooler weather and opportunities to explore mountains.

I totally agree with ALL of that!

If you are returning via Santander don’t miss the zoo park near by stop at the free site between the lake and the elephant area, it’s just down the lane

Just be aware the " elephant Aire " now has no facilities