This is not a trail you want to do with a stroller: if you're bringing one, it's better to stick to the lower part of Lynn Loop that follows the river. It is doable with a baby carrier however, and is fine for kids from about 4 and up I would say (younger might be alright too, depending on your child!).
There's lots of plant life to see here apart from the trees: skunk cabbage in the muddy, shady patches of the lower-lying areas, blueberry bushes, huckleberry bushes, all sorts of tiny forest flowers, moss and lichen, and even a fungus and mushroom or two if it's the right time of year. I've even seen chanterelles here on the trail heading up to Lynn Peak!
This is a great hike, and the park is easy to get to. There's lots of parking at the various parking lots along the road that enters the park. Facilities, including pit toilets, drinking fountain (with a tap for dogs), and picnic tables are located at the entrance. There are no facilities along the trail (unless you count a couple of benches...).
This is definitely a great trail to do if you want to see some of British Columbia's coastal, temperate rain-forest up close and personal!