Boston University published a handy two-page document (linked above) for quick reference on risky play.  

One thing I find extremely useful for an "At a Glance" reference is the paper's "Instead of 'Be Careful,' Try These Phrases" section. As adults, whether as teachers or parental figures, we tend to say "be careful" all the time. That phrase does not foster awareness or help the child grow; instead, it can instill fear or a sense of wrong-doing when children want to play.  

Risky play is crucial in the development of young children. Playing is not just play; it is about discovering the world around them.  So, I hope you find this resource as useful as I did.

What is Risky Play?

Risky play can be defined as any play that is thrilling or exciting and involves some risk of injury.—Boston University, "Supporting Young Children’s Risky Play"