Here's how Boston does it ...

Boston created a mechanism (Article 33) by which any public land could be designated an Open Space, without the restriction of terms like "park" or "garden."


This is from the preamble:

... Land can be given the OS designation, however, without the simultaneous designation of a particular subdistrict, such as "park" or "garden," where the desired subdistrict designation is yet to be determined. This system instills flexibility into the
regulation of open space.

That sounds like a really good idea. Let the neighborhoods decide what they want to do with the empty public land that directly affects them.

Here's Boston's article.