Hi
Ours are 2 and 4. We did Calais to Santander last summer over 3 weeks, down the Atlantic coast mostly.
There are some campsite chains now:
Huttopia: natural themed sites. In woods and stuff.
Yelloh Village: think Centre Parcs. Kids activities, slides, waterparks.
Our learnings:
- moving on regularly with kids that age is a hassle. Takes a full day out of your holiday while one of you packs up and the other watches the kids, then you drive 2-3 hours and again one of you sets up while the other makes sure the kids are not doing anything stupid. This year, we're moving on once a week and doing longer drives (say 5 hours instead of 2-3). We lost too many days last year moving on every 2-4 days
- yelloh village wins. The kids are so happy. There's loads to do. Water slides = happy kids = happy parents. The shower blocks are great esp in the 5 star sites. Think walk in shower where all 4 of you can go in at once and get everyone clean and dressed in one go. Not the natural country vibe we used to go for before kids but after doing one last year we're mostly doing yelloh village sites this year. You can guarantee the cleanliness of pools etc whereas some sites have one little pool full of toddlers (seeing) and guess what the kids get eye infections from the pool. I take the view that chain campsites have systems in place so this doesn't happen
See the Yelloh sites in Loire, Les sables d olonne, Landes labenne (amazing site in pine trees, short cycle path to beach)
- if you make it to northern Spain, check out playa joyel in Noja. It is on a great beach. Ferry back from Bilbao or Santander, expensive but relaxing
San Sebastian is fantastic for a one day trip and the aquarium is good for kids.
- Ile de re is beautiful but in the school holidays the campsites are overpriced and there are loads of restrictions like you must stay Saturday to saturday. Often poor pitches especially for the money. The beaches are no different to the mainland. The villages and harbours are beautiful and the cycling paths are great. On balance - we won't go back in the school holidays - not worth the inflexibility and poor vfm. It would be amazing in may/June I'm sure, and the restaurants looked like they would be great without kids!
Have fun