Wow. That’s a lot of ground to cover.
I’v driven from Edmonton to Toronto in five days. I’ve driven from New York to the tip of Nova Scotia, and then taken the ferry to Newfoundland, and the ferry from there to Labrador (OK, the mainland terminus is actually Blanc Sablon, Quebec, but you can spit into Labrador from there) in three days. If you’ve got six weeks, I can’t imagine you’ll have a real problem doing this, even earmarking an entire week for Banff (presumably including Jasper).
Some things to be aware of:
The drive between Toronto and Winnipeg is L-O-N-G. About 20 hours, if you insist on staying north of the border and going around Lake Superior, not much less if you dip down to cut across Minnesota, Wisconsin and Michigan. At least on the Canadian side, there’s not a lot to do in that entire stretch.
On the ferry to Newfoundland, get a cabin. My wife and I thought we could find a seat in a public area and just sleep there - we found that everyone who got on the boat before us had the same idea, and there were no good spots left for us. We ended up paying for bunkbeds in a barracks-like part of the boat. For the trip back, we sprung for a real cabin. The difference is tremendous.
Newfoundlanders and Labradorians are amongst the nicest people you’ll ever meet.
Nova Scotia’s city streets are clogged by the slowest drivers on the planet.
If you go to Prince Edward Island, prepare to have the image of Anne of Green Gables burned into your brain. She’s EVERYWHERE.
Manitoba uses Daylight Savings Time. Saskatchewan does not. Prepare for this when planning that leg of your trip.
Some attractions not to be missed (drawn purely from my own experiences, not even remotely a comprehensive list):
L’Anse Aux Meadows, Newfoundland
Magnetic Hill, Moncton, New Brunswick
Old Quebec City
Museum of the Bee, in Ste Anne, just outside Quebec City
Parc Safari, Hemmingsford, Quebec (near Montreal)
Ontario Science Center, Toronto
CN Tower, Toronto - looking down through the glass floor is awesome
Niagara Falls is heavily touristy, but still tons of fun
Museum of Man and Nature, Winnipeg
West Edmonton Mall - yes, it’s a mall, but come on - it’s the biggest one in the world! Also, if they still have it, the glow-in-the-dark golf is cool.
Olympic Park, Calgary - you can luge! Even in the summer!
Stanley Park, Vancouver
Have a great time, eh?