Morningside Park is a fantastic site to explore with little adventurers. The first time I visited, we went to the park's furthest parking lot (closed in the winter time) and, from there, took a large path from which we could already hear the lovely sound of water running through stones. A few minutes later, we discovered Highland Creek, a broad body of water some 20 metres wide, lying at the bottom of a valley. The stream was quite shallow at the end of the summer and its partly rocky shore attracted hikers who could walk along it without getting wet (probably not a good idea in early spring). Little clear rapids emerged through large flat rocks, while water followed a more sinuous path between the big boulders on the other side.
When we visited again in 2015, we drove to the last parking lot to enjoy the fall colours and the country road feel but returned to park in the first parking lot to see the infrastructures (playground, splash pad, washroom) and try the path from this side. The trail is now fully paved. We walked over 2 kms upstream, never too far from the river, up and down the path amidst changing panoramas. We saw murals on the pillars of an underpass and salmon in the river. I think you will like this post with my photo gallery
and more details.
I recommend rubber shoes to protect small feet in the water. While wet rocks could be slippery, I feared nothing more serious than a wet bottom (bring a change of clothes!).