I wouldn't detour to Canada just to avoid grades. Besides the air brake and transporting guns problems I believe their fuel prices are significantly higher. As someone else mentioned let the east coast mountains be practice for the big mountains in the west. Getting across Wyoming and Montana will have long grades.
If your in a hurry I'd drive interstate. Boring...yes but generally mild grades, lots of truck stops, towns and traffic if you have a break down. Also you don't have to slow down and stop at every small town you might encounter on a state highway.
If your in no hurry decide what you want to see along the way and plan your route accordingly. I'm sure there are navigation apps for truckers that would have grade information for interstates as well as state highways.
Sounds like it will be a fun adventure!
Ted