Question- Steep Sloping backyard of Rental property Liability

[Ray Slack]

Just purchased a rental property where the backyard on one side has a steep slope.  The prior owners installed retaining logs and a fence at the bottom and planted rose bushes. It's about a 8ft sloping drop and wouldn't be a concern if the new tenants moving in didn't have kids but they do..  I showed it to them and they didn't really seemed phased by it.  They later asked it I could fill it in which is not possible as the dirt would just wash away down the hill.  I offered to fence it off and they declined saying let's just wait and see if it's an issue.  I really don't think it's going to be a problem but how do I protect myself? Have them sign a release of liability? I'm at a loss on this one.

Any help?

Thanks