How To Make A Basketball Court On A Cake Ideas Of What To Do For My Boyfriend's Surprise Birthday Party?

Ideas of what to do for my boyfriend's surprise birthday party? - how to make a basketball court on a cake

Approx. 10-20 people come
It is in the park
Girls and boys will be there, but smaller
I collect the money (a few dollars per perferably $ 5) for each person, so you can buy balloons / cakes / etc

But my question is: What should we do?
What kind of games?
The park has a basketball court / skate park / Playground
annnnnny kind of advice / tip is appreciated (:
Thank you!