This year we decided to pack our own food. We feed 5 adults for 3 days breakfast and lunch for under $150. That is less than $10 a day. Above is pretty much exactly what we packed each day. I have also included a grocery list to help you adjust to your family.
It is not advertised that you can bring your own food into the park but you can now bring water bottles, refillable bottles, and your own food. We packed our food each day in a cooler backpack and reusable sandwich and snack bags.