You don't need one if it's a small family going for a walk or to play on the playground. Not sure about using the baseball diamond for teams. But if no one is there and you want to use it with your family you could.
Depending on what you're using it for but i would recommend you contact the park and let them know what you plan on doing and call the nearest police station and let them know as well. Now you've covered all bases. Stay safe
It depends on for what, and how many ppl.
No you don't exactly
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