We spent an enjoyable week on Cape Breton Island a few years ago. If you like Williamsburg-type restorations with re-enactors, be sure to spend a day at the Fortress of Louisbourg.
The 185-mile Cabot Trail loop (includes Cape Breton Highlands NP) was a highlight for us, but you might not want to tow, especially on the steep cliffs at the east. Some people base themselves at Baddeck for day trips (and to visit the excellent Alexander Graham Bell museum.)
We also enjoyed Halifax very much, for the Titanic sites, Maritime Museum and fort on top of the hill. There's a nearby municipal campground in Shubie Park, Dartmouth that worked well as a base. You can easily make day trips down to Peggy's Cove lighthouse and the town of Lunenburg.
I was impressed with Nova Scotia as an RV-friendly destination - good highways, plenty of well-run campgrounds, lots to see.