Atlantic Canada is simply a great place to take the kids: It's safe, clean, and sprinkled with just enough amusements and outdoor jaunts to keep them engaged. The provinces vary, though, in their ability to entertain the young 'uns.
Prince Edward Island is the best destination for young girls, simply due to the proliferation of attractions related to Anne of Green Gables. New Brunswick abounds with easy adventuring (golfing, biking, kayaking, big-tide sightseeing, and so on), and it throws in a handful of amusement parks and museums (a chocolate museum? Natch) for good measure. Nova Scotia might frankly be a bit boring for the tykes, though -- unless you've rented a cottage where they can swim, paddle, and hang out. And Newfoundland and Labrador is potentially great for teens with an interest in polar bears or icebergs (or science and ecology in general), but probably not much fun at all for parents with toddlers and infants -- too many miles of open space in the car for a restless baby.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.