It's incredibly easy to camp in France and wonderful too. French campsites are abundant, well equipped and beautifully kept, usually with a free swimming pool to boot! We went year after year with ours and had a fabulous time.
We did camp in Italy though not so much but again facilities were wonderful. It's a great holiday with a young family, lots of safe freedom for the kids and they can help with erecting and dismantling the tent, very good experience.
There are national websites listing all the campsites with directions and information. Find through Google. We had to buy a guide of course! Mostly you used to just be able to turn up on the day, it may not always be possible to do that now.
Wonderful times, I wish I could do it again.