We did Canvas Holidays camping lots of times in the ‘90s, I think the last time we went the kids were 11, 9 and 6. I’m not sure whether teenagers would find the lack of privacy difficult. My (now) exH would never put up with no sex for more than two consecutive nights. I guess as teens they can go to the pool unaccompanied though, you’d have the tent to yourselves for a while!
Canvas Holidays, then anyway, were leagues ahead of Eurocamp and there was another firm I’ve forgotten, who were awful too. Better pitches, definitely, and massively better camp hosts, who all genuinely understood customer service. The one year we used Eurocamp, we went end of June, the pool wasn’t heated and was intolerably cold, the pitch was dreadful, we asked to move to a different site as we and the kids were all counting on being able to use the pool every day, and the very young (19-20?) Eurocamp hosts lied about availability elsewhere. We eventually drove out to other sites and found we could have moved the first day. And we strolled past their own accommodation one evening to find them all sitting outside smoking weed. Our kids were too young to realise.
We loved the Dordogne and stayed at several different sites. South Brittany is lovely too, we liked Guilvinec. We had a great site at Royan on the Atlantic coast, but it’s a longggg slog across dunes to the beach, also lots of naturist beaches which may or may not bother your teens. The awful Eurocamp holiday was down south, near the Spanish border, and although we broke the journey with a night in Burgundy on the way down and a night in the Loire valley on the way back, it was just far too much driving with a car full of children. We never took the dog.
I think with older kids I’d go for a gîte, so there’s a proper indoor bathroom and you all have privacy!