I've never biked the Niagara Region (it's on my bucket list), but I've spent considerable time in the area over the years.

There are interesting historical sites along the Niagara Frontier, between NOTL and the Falls. Consider visiting the Laura Secord Homestead ( The Laura Secord Homestead ) and the Mackenzie Printery ( Mackenzie Printery ) in Queenston.

Although I haven't visited it in years, I recollect that Ft. George in NOTL was pretty interesting ( Parks Canada - Fort George National Historic Site - Fort George National Historic Site ). Check the individual sites for their hours, since you are travelling after Labour Day.

The bicentennial of the War of 1812 played big in Canada so you should take advantage of the history that has been preserved.

As far as routing, these links might help:

Trails & Cycling | City of Niagara Falls, Canada

Bicycling Map - Niagara Region, Ontario

Exploring the Niagara Region

Cycling

Mac's Bikes ? Bike Rentals and Tours Niagara Falls ? Bike Routes

As already pointed out, the Welland Canal is worth seeing. You can track what ships may be in the canal by checking here: https://www.marinetraffic.com/en/
As I write this, there is a laker in the Canal, along with a Canadian Coast Guard ship, and a couple of tugs and pleasure craft.

Hope this helps. Enjoy! I wish I was with you.