Another thing to consider is to put one person on a strength exercise and the other person on a cardio or anaerobic challenge. This works great for equipment that I only have one piece of.
In addition, it makes for fun teamwork. If they’re evenly paired fitness-wise, I’ll make it more like a 2-person relay. I’ll have the person who is doing the strength task do a specific # of repetitions of their exercise while the other person does their cardio. Or I’ll flip it. I’ll have one person do a muscular endurance task like a plank while the other person does 10-20 reps (depending on the exercise and how long it takes) of a cardio exercise.