As of January 1, 2015, it is illegal to:
Regarding; Children’s playgrounds and publicly owned sports fields
It is illegal to smoke on and within 20 metres of children’s playgrounds and publicly owned sport fields and surfaces (e.g., areas for basketball, baseball, soccer or beach volleyball, ice rinks, tennis courts, splash pads and swimming pools that are owned by a municipality, the province or a post secondary education institution)
For more details:
Ontario Health