It sounds like the kids were playing in their own tree, which makes this woman the worst kind of busybody (especially given that the parents were present). Calling the police was not an appropriate response, but she should have minded her own business.
If they weren’t in their “own” tree.... the kids were trespassing and the parents were allowing it. Next time the “busybody” just needs to call police and have them intervene on the property owner’s behalf.
Although we might not like what the neighbor has to say, sometimes he might be right, and sometimes not. Calling in the cops for this sort of thing can get you killed.
The woman sounds like a busybody; the parents sound like morons and the police who issued a ticket for the whole ridiculous affair sound like cretins.
(no offense to anybody)