If there are some completely unashamed people in your group then a portable restroom may be an interesting choice. A portable bathroom is inherently funny, plus using it is sure to be one of the more humiliating things that someone can experience. Nothing like being able to make direct eye contact with someone as they’re taking care of their dirty business.
The pocket sized disposable kit comes with a privacy poncho, 1 pee bag, 1 poop bag, and 2 moist wipes. Check out the video to see how you could use this on a public street with zero embarrassment.