The app from ACSI comes "for free" with the book of your choice (Europe, France, ...) but then you only get the maps for free of the country (countries) you purchased the book.
You can buy extra countries for € 1,99? I guess. Or go online to their full website and have full access to all their campings.
As for the original question: planning? When I get a direction I want to go to, I look for ACSI campings or if non in the neighbourhood, I look at Google, but the day of departure I don't know if I am going to end where I was "planned" to go to. I might as well end up somewhere completely else, depending on weather, place, interesting things to see.
Also usefull is a Michelin map (book) of the country you want to go to. There are cities marked with stars *. The more stars, the more interesting to visit. Black triangles show you places of curiosities. 3 dots mean ruines, ...
And with a California, you always have your hotel with you, so choose a direction, get in, drive, ......
Even god doesn't know where you are going to end.