Stayed in lots of them over a span of about 20+ years. Very good value holidays when you have 4 children and we have explored most of France, Black Forest, Costa Brava, Northern Italy (nr Venice) etc. If traveling a long way, then using them for overnight stops are good, but can be a few miles away from the motorways.
Have stayed in tents and mobile homes. More facilities with the mobile homes, but under canvas is more sociable and you are more likely to talk to the families in the next tent. One year, we made friends with a family from Ireland and our daughters became pen pals. Many years later, her pen pal came to my daughters wedding!
Taken my bike a couple of times and managed to escape for a few hours to explore the French roads.
If going peak times, can be extremely busy. Begins to quieten about 3rd week of August - you can tell by the prices drops. Early season a lot quieter, but weather may not be settled.
Have a good trip.