Thank you for the warm welcome and for all your very helpful comments and advice - it really is appreciated!
I think that coming from South Africa, being a crime-riddled country, we are always on high alert. And in South Africa, a simple petty-theft break-in is usually not the case as we have so much violent crime here... and so I am probably biased about crime all over the world (apologies to everyone in Europe as it's certainly not my perception of the place - we are, in fact so looking forward to the peace and tranquility of France and to get away from the crime of our country for three weeks!).
All your advice about motorways vs campsites vs aires is very welcome. We plan to stop at campsites for the most part so that we can feel comfortable enough to take our bicycles and head into the little towns to explore.
The advice about the route we are taking is also great - we are not fixed on this route (I will add our planned route in another thread so as to get some feedback on it) and have just picked something that we thought would be nice, not knowing the logistics. Through forums like this and other research, we are learning slowly

We will be travelling from the 8th of September to the 16th of September in our campervan, and so I am hoping that some of the high-season traffic would have died down by then, but am not sure if that will be the case. Either way, we are going to do a mixture of more rural areas around Provence, Aix-in-Provence, the area around the Verdon Gorge, Grasse, Calanques national park, Écrins National Park, and Annecy before returning to Lyon. A visit to the flashy coastal towns and a dip in the ocean would be a bonus but we are not overly fixed on this.
We have rented a campervan through a company called Roadsurfer and they do not have any additional security measures, and were also a bit confused as to why I was asking about break-ins 😂. We are going to stow our valuables away out of sight and locked in a hiding place in the van and, being from South Africa, we never leave anything visible in the vehicle so will be sure to put everything away and lock up at night and before we leave each day.
Thank you, also, for the french speaking advice. I am not fluent by any means but have been learning and practicing the basics - enough to begin a conversation and try before flicking to English.
I would love your recommendation for a place to stay on the coast - thank you!
Thanks again everyone!
Amanda