I've re-surveyed and confirmed there are two fireplaces, a bench, and a picnic table. I've refined the position of the bench slightly, and added the other features. I added the fireplaces as amenity=bbq because the linked example picture is closer to what these fireplaces are than leisure=firepit or any other tags I could find.

https://wiki.openstreetmap.org/wiki/File:Wood_heated_outdoor_barbecue.jpg