I lived in NB for a number of years, going to Cape Breton is not a really a beach trip, even though it is on the ocean - water will be COLD.

If beach is what you want take a look at going to Shediac and up the coast to Kouchibouguac National Park. You can stay in Moncton and take day trips to Hillsboro to see the flowerpots and tidal features, trip to Saint John to see a statue that honors the war hero Benedict Arnold and a tour of Moosehead Brewery, Fundy National Park for great hiking, you can easily do a day trip or overnight to PEI, overnight to Halifax is worth it to see the citadel and Peggy's Cove.

I hate PEI for a number of reasons, but can see why some people find it quaint and nice, just be ready to drive really slow and to vacuum red dust from your car for the next 2 years.