This backyard zip line is either genius or a lawsuit waiting to happen

So my brother installed a homemade zip line between two trees in his backyard and of course my kids went INSANE for it. We've been over there three weekends in a row now. My 10yo is fearless, my 7yo is nervous but doing it, my 4yo can't reach the handles. It's like they found the most fun thing ever invented but also I keep envisioning emergency room visits? Is this a normal dad thing to build or would you call CPS lol. No lies - best weekend activity they've had all spring though.