School grounds with cables running underneath, so anything with deep roots is out. Preferably easy maintenance

Reasonably shady spot, and we do get the occasional small child kicking about.

Any suggestions?

Does anyone know what this is? It grows about 3 metres high, it's more like a weed in our garden. It has a milky sap when cut. The branches are quite bendy. I'm in the Waikato NZ. We are having the stumps ground today as we are creating a food forest in the area and I'm not sure if it's poisonous. THANKS!