DO NOT get a car charger! You can get a USB car adapter at any Wal-Mart, for about $5. This will give you two or more USB charging ports that you can then plug ANY USB device into your car, using the device's original USB cable. Generally, I have found USB car chargers to be expensive crap, that break easily.
Mounting/unmounting, is just a safe way to deal with removable media storage. Do you just plug/unplug your USB connected device, normally? If so, don't. Take the time to mount and unmount. Otherwise, one fateful day you'll be coming back to this forum asking,
"How do I recover lost files from my Micro SD card?"