Of course the ultimate answer is yours to make, but in my practice when I’m working with a corporate client, I get individual waivers from each participant. I hope this helps.
I would utilize the exercise/liability waiver you use when training or doing any other fitness related activity. I recommend sharing whatever waiver you have with the company and get there okay, once approved by the company they can email to the employees who plan on participating. Be sure that each individual completes a waiver prior to participating. It might be a good idea to have each participant complete a PAR-Q as well.