Cape Breton Island was a highlight for us. We drove the scenic Cabot Trail and spent a night on the west side (great sunset views) plus a night at Dingwall's Hideaway Campground & Oyster Market around the tip. Steep coming down the east side, though. Some prefer to park the RV at Baddeck and drive the Trail by car.
We found one day to be sufficient at the Fortress of Louisbourg, but arrive when they open. If you have a Parks Canada annual pass, show that and you'll be waved past the ticket lines. In addition to the Fortress, the lighthouse is worth a visit. Several campgrounds in town to choose from.
A good campground for visiting Halifax is Shubie Park in Dartmouth just across the bridge. Many interesting sights - We spent several hours in the Citadel at the top of the hill to watch the daily firing of the noon gun, see marching bands, tour the fort, and see the excellent military museum. The Maritime Museum on the waterfront tells the story of the disastrous explosion in the city's harbor and has a moving exhibit on the Titanic sinking. We also visited the cemetery where many Titanic victims were laid to rest.
