Dave,
Thank you for being complete. So often similar questions are asked and there is little information to lean on.... You do say "We" and I am hoping that is two (2, dos).
My only suggestion would be "Paper Plates and such". Washing uses a lot of water when we dry camp or boondock. If you are at any kind of a festival (there are two that we do regularly) there will be plenty of trash cans to take advantage of as needed.
We eat differently than most, but we can usually buy one meal a day to save that load. We go to a 5 day event, and have only 35G of both potable and combined black. It works most times.
Matt