@Colin60 I would steer clear.
What if their insurance doesn't pay out for whatever reason?
What if they turn out to be problem guests? (you wouldn't be able to do this through Airbnb)
Just explain to them that you would be happy to host them (subject to whatever checks you make), but Airbnb isn't set up for this arrangement. Say they can go ahead with the booking and get a booking confirmation so THEY can make the claim for the accommodation and liaise with the insurance company regarding reimbursement.
You shouldn't have to have the incovenience of dealing with a third party and any delays with the money coming through.