We stayed at Braches this past summer. Nice campground. It was small and not crazy busy, even at the peak season of July 4th. Around 15 minutes to Niagara Falls, easy drive.
As far as what to do at Niagara, the Cave of winds tour is a must, you get soaked and it is an awesomw feeling to be that close to the falls. It is best just to get the package deal for all the attractions
If you are the adventurous type, the jet boat ride, ( I dont remember the name of it) looks great, the wife and kids did not want to go, so, I had to just read about!