There isn't official code for an example with playground equipment, but you could make these things with rules or insert pre-modeled assets.
If you would like to have plants in your park, in ESRI.lib, there are rules to generate a variety of plants and distribute them. Just drag and drop the rule onto a shape in your scene. Then, you can customize it using the parameters in the Inspector. Or, you could import the rule into your own code for more control.
There is an example of a garden like park downloadable from within CityEngine. Help -> Download Tutorials and Examples -> Example Landscape Design. In this example, there are rules to make things like benches, fountains, and trellises. Playground equipment could be made in a similar manner.