Yes, I think that might be exactly what you would find, Kevin! I have certainly never come across a French site that did not accept children (although, out of high season, which is when we are now able to go away, there usually are very few children on sites).
French children on the whole are extremely well-mannered and well-behaved. I don't know whether the fact that they are much more fully-integrated into society as a whole is the cause, or the effect of that, but it is certainly the case. French families seem much readier to take their children to, for example, decent restaurants, than are most parents this side of the channel, but having got them there, they do demand good table manners and some sort of contribution to the general conversation.
Given this situation, why would anyone want or need separate provision?