[Ceratopsians grazing in front of Royal Tyrrell Museum, Drumheller, Alberta. They are scary but harmless, but do NOT get between a mother and her calf or she will show you what those horns are for.]
Butte to Prince Rupert and then to Newfoundland and the Maritimes is a loooooong way. 7K miles may be underestimating if you do any exploring along the way. Speaking of provisional speculations insensibly morphing into plans, setting out to see all of Canada in a summer can very well suck you into seeing how far you can drive every day. I guarantee you the inside of your car is nowhere near as interesting or beautiful as Canada, which, to some tastes, is the most beautiful country on the planet.
I remember driving the backroads of northern Alberta (south of the permafrost) and coming up with a hallucinatory theory that heaven is not in the sky but in certain locations on earth. They aren't publicized and one can only find them by stumbling on them inadvertently. If they became well-known they would be swarmed with tourists, motels, souvenir shops, gas stations, crowds, and fast food. In short they would become hell, which is also here on earth. Some parts of heaven on earth are protected by their elevation or remoteness or the policies of the US and Canadian national park systems. Other parts are protected in part by their remoteness and by the fact that most people take the main roads and by the fact that most people can't see what's in front of them, or it just doesn't appeal to them. Heaven may be an individual phenomenon. I understand neither theology nor psychology, but like philistines everywhere, I know what I like.
Plumas County on the east side of the Sierra crest is such a place. So is northern Alberta. It is big family wheat farms where the farmer, the family, and one or two farmhands work the place themselves. Here in California agriculture is conducted by corporations controlled by much bigger corporations like Safeway and Lucky. The fields are worked by peons so alienated from their work and their situations that they are kept literally illegal. The difference between that and prosperous Alberta farm families working their own land is staggering.
You have long since heard my rant about the ignored-but-obvious connection between the numbers of illegals and the US policy of penalizing the illegals rather than the employers. Canada penalizes employers who hire illegals so there are no jobs for illegals and therefore no illegals. There are plenty of legals, usually educated Indians, Chinese, and Pakistanis in Vancouver, just no illegals.
Among the vast expanses of wheat are a patchwork of non-arable land left as large stands of poplar and pine, dotted with ponds. These are home to the occasional moose or bear or skunk which wanders onto the road. The cars are few and the drivers respectful so the local tetrapods wander as they will. The towns are small - a diner, a dying motel, in the larger ones a gas station, and a few stores run by people clearly doing it as a part-time job because they can't stand the thought of moving to Calgary. Occasionally there is a small lumber mill or a horse farm with pintos.
If you are in a hurry to get somewhere, you will miss this. Worse, you might see it and not get it. Slow down and wander.
The bad thing to avoid, (I assume you know this but just in case, I will warn you anyway) is Canada Immigration. They are unmitigated assholes, AND they have real authority over your life. They were, with few exceptions, the only genuinely nasty people I met in Canada. If you tell them you want to "see Canada" or "wander" or whatever, they will shut you down and give you an impossibly short visa. I suggest strongly that you have a printed-out itinerary and dates when you plan to be in each place.
Google Prince Rupert so you can specify what tourist attractions you plan to see there. Google Prince George and do the same, and so on, all the way across the country, assigning dates to each place, and including the tourist attractions on your itinerary. It makes no difference whatever whether you actually do any of the things you said you would do or even go to the places you said you would go. But the bastards (many of whom are thoroughly unpleasant young women) will gleefully cut you off at the knees if you don't specify all that crap for them. Generalities will NOT work. You must have a detailed list and dates. Invent a cousin in Halifax. Visiting a former professor is definitely the right thing to tell them about.
I hardly need warn you, you must have NO DOPE in your car when crossing the border in either direction. As I understand it, if they find marijuana they will detain you for several hours and then turn you back and never let you into Canada again as long as you live, which is far worse than a minor bust would be. The search is more thorough than going into the Soviet Union used to be. Israel puts some serious searching on your luggage too but they aren't looking for recreational drugs. The US border patrol does a thorough search as well. I suppose this is all since they caught some assholes trying to cross into the US from Canada for the purpose of blowing up something in New York a few years ago.
[Rita and I have an enormous bulldog named Oliver who is sleeping on the floor as I write. As bulldogs will, he just cut an enormous fart so I have had to pause and open the windows.]
Anyway, consider going slower and covering less ground. I don't know if you have any interest in paleontology, but even if you don't, the Royal Tyrrell Museum in Drumheller, about 80 miles northeast of Calgary, is by a large margin bigger, better, and more interesting than whatever is the second best dinosaur and giant-extinct-mammal museum in the world. Definitely worth a day of your life.