UI and elderly users

I think this will do what you're looking for: You need to add a google maps widget to your home screen that will launch it into drive mode (which is a weirdly obscure way of doing it). So, long press on an empty space on your home screen and bring up the list of available widgets. Scroll down to "Maps" and select "Driving Mode" which should add an icon to the home screen. If you now launch gmaps using this icon it should enter driving mode. Just swipe down the field at the bottom of the screen and it should be full screen.