Honestly I think it’s partly about mindset and leaning into the concept of Type-B fun. Like the way hiking is a bit miserable and you grumble and wonder why you’re doing it, until you see the view at the top and then try and convince all your friends to try it too. 😂
Mobile home parks worked well for us. I always recommend self catering near a restaurant for the flexibility with small ones. Work to their schedule, and don’t expect them to fit around yours.
We drove to France, and brought a baby gate for the deck, and a small paddling pool when they were really wee. We booked a mobile home with an extra bedroom and made a play area out of it, without us all living in permanent toy clutter chaos. Up early in the morning, to the pool, playground or beach, then back to the mobile home in the hot afternoon where they could play indoors, and we sat on the deck and read, or watched a movie. Then back out again about 4pm.
They slept well with all the exercise, on hot days we would go for an air conditioned drive, do the odd day out. If there was an attraction we wanted to see, we spot each other with the kids. We often ate late- a take away pizza and a bottle of wine on the deck after they were in bed. Not the most exciting of holidays but they worked for us.
The Vendee has a nice climate - a bit warmer than you’d expect for their position and not as long a drive for similar temperatures further south.
Because we drove we could bring our own home comforts, bedding etc and we saved quite a bit by booking directly through the campsites rather than through euro camp. Our packing included stick up blackout blinds, a fan, and a kettle. I didn’t mind going a load of laundry or two, so not as many clothes. For kids: rash vests and peaked hats are essential. Saline sachets for sand in eyes and Baby powder for getting it out of toes. Being a beach tent.
Obviously if cooking and laundry are going to spoil your holiday, none of this would work for you. Every year we booked a family summer holiday and a couples weekend so we had some adult fun to look forward to forward to if we were having a particularly grumbly day.