This is a question where the law is a little vague. Look at the commen sense of it. Your not in a parade, your in a public park. It is not in a sheath, it is being wielded around in a public park, where children play. I'm sure, you would attract unwanted attention from many, who would guaranteed be on their cell phones in a minute dialing 911. Where the law is vague, it may not be vague that your inciting a lot of nervous people, meaning causing a disturbance, nuisance, endangering wellfare of minors in some eyes. I'm sure if you weren't arrested for something, you would be asked to leave and not return brandishing a weapon. All of which, you would be better off avoiding. I know if I was in a park with my child and saw someone, waving around a sword, I would leave. Hence, would you want families to be frightened, though that wasn't your intention. Practice in a more practical setting, like a dojo, or backyard or big room. Why risk it?