Keep in mind there is Humber Bay Park East and Humber Bay Park West.
I feel the East side is much better.
I've been coming here since I was a kid. Awesome place to go for a walk. The views of downtown and the lake are amazing.
There are boulders that line parts of the shoreline that you can walk on. You can also skip rocks on the beach.
There are little ponds here and there that look lovely.
My one complaint is that parking isn't free from roughly May to September. This is only at the East side. I don't know what the parking situation is like on the West side.
The West side has less green space. There are some boating clubs/docks.
If you have the time, check out both sides. If you're pressed for time, I recommend the East side.