DO NOT over think it! Relax and enjoy yourself. One of the biggest mistake a lot of people make is to over pack. We live by the simple rule that if it is not used in 3 trips, it goes out. Make your first trip close by or at least near a Walmart in case you do forget something. As suggested, keep a running list with pen and paper.
As for food, we do all of our cooking outdoors, so think grill and camp stove type items. One thing I did was to create a "meal Planner." Its not a hard rule to stick with but it helps when shopping to know what we need. We don't over buy at the grocery store