This week for your car kits, add a blanket (or 2) or some towels. These especially come in handy if you break down in the winter, or for simple things like an impromptu picnic or wiping water off the slide at the playground - they're just nice to have in the car. These probably won't fit in your box, but if they do, great!
How is your three month supply coming along? Once you have your gathering complete, you need to have a method for keeping track of it all and staying on top of it (of course, you should have a method even as you are gathering, too). I like to keep a small notebook right outside my closet doors. Every time I take a three-month-supply item out of the closet (whether I'm making a food storage meal or not), I jot down the item on my piece of paper. Then, when I go to the grocery store, I can just tear off the piece of paper and add those items to my grocery list. This way, my three month supply is constantly full. When I add the new food to the closet, I am also sure to put it in the back so my food never goes bad.
We're still gathering RICE for our longer term storage this month. Get what you can. Rice is so versatile and can be used in many different types of meals.