A continuous marked hiking trail runs from Swallowtail (eastern most tip of Northhead) all the way to the Whistle lighthouse on Northern Head. Doing the entire trail is a major adventure, but it is quite possible to break it into different parts for an enjoyable and less strenuous morning or afternoon hike. We did run into a young couple who had done essentially the entire trail later in the week on Ashburton Head - they were looking for a ride back to their car at Swallowtail ...;-)
For ease of parking, we opted for the day pass at Hole-in-the-Wall Park (a private campground) and bought their more detailed internal trails map - which was a good investment. Starting at the eastern-most observation deck we followed the hiking trail along the coast to Hole in the Wall, and then took the Park's internal trails and roads back to the car. (You need the day pass to use the Park's inernal trails).
Without a doubt, it was one of the most interesting and visually stimulating hikes we took. From the other side of Whale Cove, you can get a better understanding of the topography - a series of rocky fingers extends out from Fish Head to Whale Cove Beach, with Hole in the Wall being the second to last.
You get excellent views of of fishing weirs, great sightings of seals and whales (if your timing is right) - and of course panoramic views of the Bay of Fundy and at least the ferry making one of its runs to or from Blacks Harbour. The trails from Fish Head to the beach are moderately challenging - a bit slippery if it has rained recently, but otherwise straightforward.
We did up the difficulty level by climbing down into Grotto Cove, since the tide was going out - and made good use of the rope "railing" provided. We should emphasize with the slippery rocks there is considerable risk involved in the climb down and back up. This is not really a "family: portion of the hike! Not many do it - and the reward at the bottom is pristine rock collecting opportunities. Climbing back up with pocketsful of rocks was - well - amusing in its own way. One of those life lessons you might say ...