We've recently come back from two weeks in Carnac in Brittany (2 small kids, elder 2 1/2 and the younger 10 months and we had a ball. I'd heartily recommend it for small children. Some things that we found that may resonate with other parents of young kids.
- We travelled in our own car on the ferry. No hassle at airport, had our own car seats, could load up lots of gear -- buggies, etc, able to bring back some goodies. Travelled with Brittany Ferries, took a cabin - v. pleasent journey.
- Took a mobile home in Carnac on nice campsite. Easy to maintain. Campsite had a toddler's pool, access to the beach and plenty of nice playgrounds for the kids, and plenty of other small kids around, so our two were both well occupied for the fortnight.
- Weather was normally in the mid 20's and sunny. Had two wet mornings, so no great fussing with sun-creams, etc.
So, all in all, we all had a pleasant couple of weeks. We intend returning next year with the kids and we'll probably bring the dogs (another advantage for us - both Brittany Ferries and the campsite are sufficiently geared for dogs to make bringing them possible).