Re: Small park? Square? Small public garden?
I'm not much of a city girl, but my brother lives in Toronto, and just down the street is a little park with some playground equipment, benches, grass, and paved paths, and the entire place is probably 1/3 the size you describe. I'd call it a park along with the others here. A park is defined more by what you do there than its size, I think.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.