+1 on Cheticamp - great place to use as a base for the area - lots of trails and excursions to take in from there. Definitely hike the skyline trail and make sure you drive the Cabot Trail in a clockwise direction. You may want to leave the trailer at the campground and drive the Cabot Trail in a day (a long day but definitely worth it!). The grades are steep and winding, so going through it without the trailer is much more relaxing. Please make sure you take in a Ceilidh (Kay-lee) while you are in Cape Breton; a great musical experience.
Further south, the Bridgewater area is very nice (Lunenburg). Lots of great food and scenery.
Be warned, the distances between areas are deceivingly long - so the distance from Halifax to Cape Breton is a decent day's travel.
Our favorite place to vacation, and we will definitely be going back again.
Enjoy!