If this is the actual question, I would modified the exercise session into Sitting Volleyball. So no one, even the participant who has an amputation, will feel excluded. I also want to host this event to show that we can play sports in multiple ways.
There are multiple scenarioes to this question. For instance, the participant can feel sick on the day of the program, or the participant is immobile without a wheel chair. As long as you say how you would modified the activity, such that your participants enjoy the program and none of them feels excluded.
*If you want to sound ultra-smart, add "modified intervention." This is an OT term meaning that instead of forcing and training the patient to do an activity, the OTs provide tools to assist the patient to do the activity. For example, if a patient cannot bend his back and wear his socks, his OT would give him a sock-aid, so he can still wear his socks independently.