does anyone have any experience of crushed walnut shells as a ground cover alternative to a lawn?

I have only seen it once before, and there's very little about it online.

My specific concern is if my son could play soccer on it. A lot of people in my area are pulling up lawns and landscaping with decomposed granite, but I wouldn't want my son playing ball on the stuff. Too slippery, and could easily cause scrapes during falls.

Thanks!