A cheap answer for the dinning tarp is a bit of tarpology.
All you need is a standard tarp, 4 oars, 4 throw bags, and 4 bungee cords.
As long as you are running multi day trips you probably will have all of the quantities needed except the bungee cords.
Start out by finding the middle of your throwbag, go to a corner and wrap the tarp around the our handle and then attach it with a clove hitch with the bungee cord, attach the throw rope to both ends of the bunge cord. Then tie both ends of the throw rope to anything substantial. i.e. trees, bushes, big rocks, anything really. Repeat the same on each corner, make sure each rope is pulling away from each other and taught.
Now you have a cheap and easy kitchen tarp.
The reason for the bungee cords is that you will have winds blowing up and down the canyon as the day heats up or cools down, and if you get some really strong gusts the tarp can rip out because it is static, with the bungee cords it creates a dynamic tarp, also it helps keep that noisy tarp from flapping to much.
Enjoy the joys of tarpology