Keep a couple of beach towels in the truck; the bigger, the better. If anyone gets a serious cut, you can use them to apply pressure and limit the bleeding. I went through a glass door when I was 5 and a couple of beach towels saved my life.
I read another thread about a customer complaining about an employee peeing on the job site. I was buying a first aid kit the other day (thanks to this thread) and in the same aisle, they had those bottles you pee in when you are bedridden in the hospital. I put one under the seat in the truck and can discreetly use it if needed. It was about $7, so there is no need for everyone to share the same one.