Here's what I have to offer based on one experience.
For me flying from Boston to Toronto, then to Halifax was much cheaper, but circuitous. Playing St. Georges in Toronto made that completely worthwhile, however. Once in Halifax you have a 3:45 drive to Inverness. We drove from there to Ingonish and back, about 3 hours from Inverness to the tip of Cape Breton.
I have not done the drive, but have been told by one guy I met from Boston who makes the drive 4 or five times a year (his wife is from Inverness) that you can make the drive from Cambridge to Cabot in 11 hours. I will be going up there again, for sure, at some point in the next year or two and I intend to drive next time.