I pony extra horses a lot. It's no big deal. I've had to let each horse learn what a lead rope under the tail is, that they can't kick the horse I'm leading etc. It's all part of the process. But they learn.
Horses don't seem to get as worried and want to kick if they moving at a walk. If you speed up to a trot, they start wanting more space and are more prone to want to kick their neighbors. So you may want to start at a walk and every time you see them start to lay back their ears or give signals that they may kick. Box their ears or ask them for their attention, Pretty soon they forget about the ponied horse and pay attention to you.
My daughters have grown up and I don't always have enough riders for all my horses. I pony a spare so I can give them all some exercise. Sometimes I change the saddle half way thru the ride, Somes times not. My horses have done this since they were foals. I often rode their dams with the foals at their side, so the youngsters would learn to pick their feet up over roots, rocks, and water crossing.
Here is a Youtube video from last November, We are just walking, nothing fast but both Dave and I are ponying an extra horse. We had brought 4 horses down for the ride so my wife and daughter could join us, But on this particular day, it was just the two riders.