It's interesting that you should post about this... Earlier this year, the son of the Hamilton County Prosecutor (where Cincinnati is located) was brutally attacked at a bus stop following the "Taste of Cincinnati". I didn't attend, but I looked at the website for the event and saw that weapons/firearms were prohibited.
Since the fireworks are coming up next week, this morning I decided to follow up with regard to the "rules" for WEBN Fireworks/Riverfest. I found a different page than you did (http://tinyurl.com/mve95m3), but sure enough, "Weapons of any type" are purportedly prohibited. I called around and found a "Specialist" in the special events section of the Cincinnati Police Department (CPD) who told me that a) yes, firearms were prohibited, and b) that since WEBN was renting the parks, they could do what they wanted.
It was clear between he and I that the law department would need to be my next point of contact.
Following up on communications I had with the law department earlier this year after the ToC event, I wrote back to the woman who had provided me with information, only to find that she was no longer worked there. So... I wrote to the City Solicitor and the Chief Prosecutor for Cincinnati. I put them on notice of my intention to carry at the event (much like I'd previously done for the Open Carry/Firearm Education walks at the University of Cincinnati and The Ohio State University) and asked them if there would be any attempt to cite me or remove me from the event for carrying a firearm.
We shall see.