Where to go with kids? By ferry to Calais-where next??

[Howmanysleepstilchristmas]

I'm looking for cheap summer holiday inspiration! We want to travel by ferry/ car to Europe, and can drive up to around 7 hours/ day. I get 2 weeks leave, and would like a 2 centre holiday, or more, stopping for a night-4 nights to break the journey if needed. Recent holidays have been Brittany/ Ardennes/ Netherlands.
The kids are 3,4,9 and 11. I'd love to take them canoeing/ bike riding etc, plus the 3 year old is keen to visit a beach at some point!
Cost is a huge limiting factor, so less expensive areas would be good...
I'm a bit unsure where to start looking. Any inspiration welcome!

Duinrell is good and beekse bergen in Holland. Both easy to get to from Calais and great for kids.

I second Duinrell if you haven't already been. It's really easy to cycle to other towns and the beach if you get bored of the amusement and water parks.
We went to Camping Fuussekaul in Luxembourg recently. Lots of activities to partake in and a really beautiful country.

If it's canoeing you want, you should head to the dordogne! You could stop somewhere central on the way down - Paris even? Loads of campsites or holiday rentals in the Dordogne to keep costs down and generally good weather.

I would say the Vendee. Dordogne is more than 7 hours from Calais, but you can get to the Vendee in 6.5. Beaches, canoeing, bikeriding all possible, plus the bonus of the Puy du Fou and La Rochelle (if you go South Vendee)