Now you would think I would know the answer to that question as I just left Niagra Falls and am now in Erie PA but that was not the route I had taken.
I can tell you that as you pass thru the Cattarauqus Indian Reservation on Route 20, just past Irving, be sure to fuel up as diesel is a lot cheaper on the reservation. Also just east of the thruway at Hamburg at 5533 Camp Road there is a new Camping World store. And while you are at Niagra Falls visit Smokin Joe's on route 31 East of I-190 for another reservation fuel stop.
A couple more hints..
If you go into Canada use the Rainbow Bridge at the falls. Avoid the Peace bridge at Buffalo and the Lewiston Bridge unless you enjoy sitting in bumper to bumper traffic thru customs. The Rainbow bridge is busy but not nearly as bad as the other 2.
Went into Canada 3 times and the only ID required either way was a photo id such as a drivers license.
As if the American and Canadian sides of the falls isn't enough to see here is a suggestion..
If you have the time a recommended side trip would be to Lockport NY for the
Lockport Locks And Erie Canal Cruises.
The Lockport Caves and Underground Boat Ride is another interesting attraction. After the cave be sure to take a tour of the same locks that the canal cruise went through. There also is a 2 hour round trip train ride to Medina and the
Medina Railroad Museum. The Museum is one huge collection of artifacts and memorabilia as well as a huge HO scale layout.