Have you tried the FCC database? that is always a good place to start. Then the search function, it's Google built into your scanner. Is this Westfield Stanley Park a city owned park? If so they may use city frequencies.
It's a privately owned and operated park in Westfield. They could be using a trunk system, VHF or UHF portables, or anything else. The best way would be to go there with a scanner with the Close Call feature and see what you find.