"The beaches east of dartmouth (Rainbow Haven, Lawrencetown, Martenique, Clam bay) are nice (though the water isn't real warm)"
lol...that's an understatement! I grew up in Dartmouth and when I was little, my family used to regularly visit Martinique Beach. I was never able to go past ankle-deep in the water, my feet would literally turn blue. It was always fun digging for fresh clams though, and then roasting them on the beach.
As for places to visit, in Halifax I'd recommend The Citadel, Point Pleasant Park, The Public Gardens, The Maritime Museum of the Atlantic. The Historic Properties along the waterfront is a really nice touristy area. Outside of Halifax there's always Peggy's Cove, the Annapolis Valley (absolutely gorgeous scenic route, esp. The Lookoff), and the Cabot Trail in Cape Breton. I'm not sure about travelling with a dog...you will need to plan ahead and see where your pet may or may not be welcome.