What should we expect to pay ? French campsites

[travellingtime]

Currently researching campsite for first overseas camping trip 'en famille' which will include me and dh, plus dd-2yo and ds-5yo. We will have a campervan with awning. Will need elec hook up too.
I am looking around La Rochelle area, pref a site walking distance from beach, though not essential. Would like a site with pool(s), shop, poss some entertainment for kids, restaurant and/or take-away, but not necessarily with evening entertainment etc.
What can I expect to pay per night?

Oh, this would be in August, btw.

We have paid ?500 for 11 nights in August from the 13th. We are a family of 5 though.

There isn't a set formula for this and it really depends on the camp-site. Often the pitch may be for 2 people and you pay extra for additional family members. Your probably would not have to pay for a 2 year old - but may have to pay a child rate for the 5 year old. We are now having to pay an adult rate for our 12 year old on most sites!
Some sites have pitches that include electric hook-up (could be typically 2 - 6 euros per night) and for others it is included as part of the package. There may be additional charges for credit card booking fees and the French have an added tourist tax (but this is quite small).
I would say about 35 euros a night for a 4 or 5 star camp-site and about 30 euros for 3 star.

For a 4 or 5 star peak season (i.e. July to mid or end of August or even 1st September for some) you would be looking at upwards of 50 euros a night including electricity (we're paying about 56 euros for our pitch from 19-25 Aug). Off season, some of the same sites using camping cheques or the ACSI discount card (some sites take these from mid Aug) can be had for as little as 15 euros including electricity plus 3-7 euros each for the children). Smaller sites or municipals are significantly cheaper, we will be overnighting in Macon at just over 20 euros for 4 of us (no electric).

Camping in France is not as cheap as you might think high season but you do get your money's worth There is so much to do on the big sites you don't end up paying for any other attractions or entertainment. I don't begrudge paying £10 more than I would pay for a small pitch on field with a compost loo in Sussex for a massive pitch on a site with an amazing pool complex, kids club, several playgrounds, archery etc etc

The 30-35 euros a night was just for the pitch with 2 adults and one paying child. The cost of electricity, booking fee (typically 5-10 euros) and an additional child, if you need to pay for the 2 year old (typically 5 euros) would make it 50-55 euros in total.