Does anyone know if this would be safe for a very advanced 4 yr old?

Warren Falls : Yes, it's safe for 4 year old kid.

Depends on the 4 year old and your parenting style!

No, not safe for a kid.

its safe at low elevation but I would have some concerns over looking the falls.

If you hold his or her hands and don't let your child get ahead of you, you should be fine. It's pretty safe.