have you thought about camping in France - you can drive so can take all the important things for the kids (precious toys etc!) it's a very outdoors life so they get tired and tend to sleep! All geared up for kids and the food and wine are great! very laid back and realxing. We;ve taken our 2 since they were babies and they love it. Been to Butlins too - kids loved it (especially Bob) but not really my cup of tea!
Oh, when I say camping in France, i mean in a mobile home!!! I personally couldn't do a tent especially not with 2 toddlers!
We go beginning of Sept and the weather has always been fab and we only go to S Brittany/Vendee.
If you go with French Life you can use your tesco clubcard vouchers and get 4 x their value!