I'll second the point on bears if you're heading for Yosemite, Sequoia/Kings Canyon, Yellowstone and many other parks with a bear issue. Not only is it illegal to leave food in your car (and the bears will definitely smell it in the trunk), you can get a fine of $5000 in Yosemite for doing so (we were just there and saw the sign and were even made to sign a piece of paper saying we'd been warned and confirming that we would remove all food and place it either in bear lockers or inside a hotel room).
You should make sure your food is packed so it's organized and easily moveable. Also, don't forget how hot it can get in the trunk - that will accelerate the deterioration of many foods.
In any case, sounds like you have a great adventure planned - enjoy.