x2 on the KOA in Niagara.
Just a couple of other suggestions for you:
1) if you go thru Montreal take AUT30 when you hit the city, it is a bypass and will reconnect with AUT20 on the other side of the city and avoids all the traffic, AUT20 will become 401 in Ontario and take you all the way to Toronto.
2) I took 2 different routes when we went out east last summer (via Ogdensburg NY and across US2 down and via Montreal on the return), and I much preferred crossing the Ogdensburg route. The drive across US2 is slower, but so much more scenic and it will also take you thru Adirondack National Park, Lake Placid and Mennonite country near Ogdensburg. The AUT20/401 drive is just flat and straight but quicker.
3) for either route (via Montreal or Ogdensburg) we stopped at the KOA in Mallorytown Ontario (just west of Ogdensburg and about 2 hours west of Montreal). It is an average KOA, but we really liked the hosts, so much that we would consider going back just for weekend trips.
Rob
rvtechwithrvrob.com