We went with Keycamp to Brittany last year. We stayed in a Grand 29 3 Bedroomed. It was me, DH and 3 children aged 6, 4 and 2.
Yes, the caravans are cramped, particularly as we are used to a lot of space as our house is large but it didn't bother us in the slightest.
Fortunately we had fab weather, so we ate out in local restaurants or had barbecues. We ate all our meals outside on the patio furniture supplied. We literally used the caravan to sleep in and that was it!
The facilities and campsite was excellent.
We have booked to go again this year - but this time staying in a Grand 34 3 bedroomed, purely because it has an extra bathroom.
Personally, after having a look around the Eurocamp caravans whilst in France, I found the Keycamp ones a lot nicer.
A friend of mine who has 5 children ranging from 3 up to 12 has always done the Keycamp/Eurocamp/Eurosites holidays. She prefers the Keycamp caravans and she manages to get her 5 strapping kids fitted in LOL!