Packing as minimal as possible - how to survive 4 days?

[TheThreeS-kateers]

We are hiking into a campsite, about an hour or two in. We're amateur backpackers, and we've got a lot more experience as simple drive in campers/canoers/kayakers. As we are students, both of our main camping gear is several provinces away but we can't help but want to get out in the wilderness.
We have two large backpacks and our dog's backpack (can hold about 12lbs for her).
What are the essentials for surviving 4 days eating-wise? How do you keep things cold... if even possible?