A completely fenced in off-leash dog park is visible from the parking lot:

This is the kind of dog park your trainers warn you not to visit with your dog: a wide open space wtih nothing for the dogs to do but get into trouble with each other.
There is a wide gravel trail running alongside the park. The walk along the trail going south-east is pleasant enough. Two-meter tall bullrushes flank either side of the trail in some places.

The trail ends at the entrance to the St. Clair subway station on Tichester Road, one block north of St. Clair and east of Bathurst. You should be able to walk from the dog park to the subway station and back in about 30 minutes.
There is a water fountain for dogs next the tennis courts west of the dog park.