not been here but unless it's a one or two star site you will have very little problem with cleanliness 98% of the French sites we've stayed at have been 3* or higher and were spotless with good security and had plenty to do for the kids and if hte older ones can speak a little French there is usually even more to do

Though it does go a long way if you encourage tehm to pseak French whilst talking to campsite staff you will find them even more helpful as they give you respect for trying

stayed there last year (july) in site own accommodation (3b mobile)for 3 weeks - had a great holiday and would recommend it.
We had 8,6,4 and 1 year olds with us.
Site was small which was fine but a bit cramped - eg no big open play areas for football or kite flying. Apart from this it was great.
Pools perfect for kids & adults - small enough that you could see young kids in baby pool and the older ones on the slides (which where great for 8 & 6 year old boys who are not timid but where not so big that you would worry about them on the slides). Also indoor pool good on colder days but all days we were able to use outside pools.
lovely path walk along shore to port bourgenay from the site - difficult to use pram on it as a lot of it is sandy
lovely sea cove next to site with rocks to explore not suitable for swimming for young ones though but there is a bus to 2 great beaches from the site - sables d'olonne is a fantastic beach for small kids although it is busy and bus is best as you dont have to find parking.
Some great cycling from site. the first bit towards port bourgenay is on a b road with only some cycle track but there is a rough track runs parrallel - can hire trailers on site for younger ones. We and 8 + 6 yo cycled to talmont chateau and spent few days doing a forest, beach, picnic, marshes tour all within 10-12 mile round trip. Bourgenay is a holiday village - very nice one - so most of facilities are for residents but it is nice place to visit and walk to and through.
Could go on but best if you ask any specific questions that you have. I wished I could have got some detailed information last year before going as we were betting 3 weeks and 3 families holidays on it but we weren't dissappointed.
Noticed on your thread that you have been to Carnac la grand metarie how would it compare for activities within walking and cycling distance from site - interested in trying somewhere different this year that site looks good but looks very big and of course Brittany weather can stop a lot of pool or beach activity! Would be interested in your views as your kids are similiar ages.

Thanks very much paddyl!

We've gone ahead and booked Le Littoral now - sounds like we've made the right choice!

Which of the local attractions would you most recommend? There seems to be so many - though I'm not sure which ones would be ok for 3yr olds.

La Grande Metairie is an amazing site. The on-site activities and large layout of the site means that (in good weather certainly) you may choose not to leave the site! We didn't get to use the outdoor pool much, it was too cold - we went in early July a couple of years ago and hit average weather. The indoor pool was good though with a separate kids paddling pool with a little slide, and a jacuzzi. With regard to the site's location, it's right in amongst the 'stones' - the alignments which attract a lot of visitors to the area and really are amazing. I don't recall any specific bike paths, we cycled on the roads with a then 7 yr old and a bike trailer we hired from the site. The roads were pretty quiet though. The beaches at Carnac and Trinite Sur Mer were both really good - never had a problem parking.

There's lots of lovely places to discover nearby - although by car is best, you can cycle around the stones and off along local roads to discover other woodlands and more alignments often hidden away - other than that we travelled by car to reach things - the campsite itself is a 10 minute drive away from Carnac itself. I would definitely recommend it, but as you say, you probably can't rely on the weather as much as you can in the Vendee (I don't really know, having not yet visited the Vendee, but we're going there this year in the hope of getting better weather!).

We went back to Carnac again last year and stayed at a smaller site with less facilities but had a lovely time also - we had taken our own trailer tent to la Grande Metairie, and last year we had this other sites own mobile home which was lovely. Whilst we were staying there we checked out the Grande Metairie's prices for their own accommodation - but it was much, much higher - an extra £2 - 300 for the same two weeks - you're paying for the facilities on-site obviously, but you need to decide how important they are for you!

Hope this helps!