An awesome family hike (and also a visit to a famous tourist destination) is the Hopewell Rocks in New Brunswick. It is a fairly easy hike, but not one that allows for strollers as you will be walking on the ocean floor! It is perfect for those using front or back child carriers. We used our Deuter Kid ComfortIII. It was fantastic! The hike in is on a very wide, very well maintained trail. It was beautiful! There were a few steep areas off the main trail that allowed you to look out at various rock formations. At the end of the trail is a very large staircase down to the ocean floor.
What we found ideal was to hike in at high-ish tide and take in the view of the rocks semi-submersed, have a picnic lunch, then when the tide was low head down to walk on the ocean floor! It was perfect! Our wee one was 15 months when we did it, and even at that age, she loved seeing the rocks and water. After hiking from the stairs past Diamond Rock, H was asleep on my back so it was a nice time to take it in and chat with my partner.
All in all, I would say plan a whole day for it; take your time. Have a picnic, play in the play area, enjoy the mystical scenery of the Fundy tides! Not just anywhere can you walk past rocks as tall as buildings with seaweed taller than yourself!