My secret shame is that I am/have livesd SO CLOSE to this place for many many years and never visited before. My friend and i went a few months ago (late reviews I know I know). just to walk around, get a great view of the city, CN tower, walk the little paths and just chill.
They have a restaurant here (it was closed by the time we arrived so can't comment on the food) if you want to enjoy some of the local fare after walking around here. They also do some small plays by the pond I was told by staff. What a unique space in Toronto. Parking is limited but I believe there are shuttle busses from particular subway stations (check the website for specifics).
They have a sustainable garden centre and market that offer up unique items for sale.
A great place to spend an afternoon :)