Traveling from Texas to Virginia while one of us uses oxygen continuously. Any advice?

I am going to check with our oxygen supplier about precautions, supply of oxygen and storage of tanks in the car. I was thinking about plugging up the home unit in the car and then using tanks while out eating and visiting. They say to leave the window cracked a bit. And to never store tanks in the trunk.. Anyone have any additional hints. My husband is hopefully going to see an ex Korean war buddy after 25 years!