I lived in upstate NY as a kid and moved back in my career. Never went to Niagara falls when I lived there or as a kid. Took my boy up last year because we had to split vacations between the wife and I because my dad was living with us. Since we were in the Finger Lake region, my boy wanted to go to Niagara.
DO NOT GO ON A HOLIDAY!!
We went early August, week day. I paid for a tour. I'm glad I did.
When I saw the crowds on a weekday, the tour guy said this was nothing.
Will say the next time we ever go up there, I'll get a passport and do the Canadian side. Way much cooler on the Canadian side IMO. Ironically, when I lived in NY, I was only a short drive from the Canadian border and never needed a passport back then.