@Rhonda439
Hopefully a Host that does offer these as experiences can chime in here? I'm not familiar with Airnnb's Experiences, but I have heard other Hosts discuss liability waivers for them that guest sign.
That said ATVs especially have a high incidence of injury and deaths associated with them. I'm not sure any insurance company would cover you even with liability waivers, but you can ask. Not sure about Aircover for Experiences, but you can do your own research by reading through whatever help articles are out there.