This app was mentioned in 2 comments, with an average of 2.50 upvotes
aye thats the best thing to do then you only have the rucksack to worry about. make sure youve got a good torch/head toch and download the car finder from the play store... saved me stumbling about trying to find my tent at many a bike do ;)
Here you go, lots of cool features like automatically saving your location when your car's Bluetooth unpairs. As far as parking locations go? I enter my destination address in my gps, then select Stopover->Near destination->Points of interest->Parking
I don't see the issues you're trying to solve with that other then the fact that half the places people park near public parking is restricted paling, which means multiple people will park there, along with street sides during specific hours, etc which your app will all think is available because more then one person parked there that one time?
https://play.google.com/store/apps/details?id=com.edwardkim.android.carlocatorfull