Hi, and thanks for your contribution! Since you requested a review, I went over the changes you made. I think in this case you could use either playground=swing or playground:swing=yes. While playground=swing seems to be much more commonly used, I'd consider that to be more appropriate for an area that only has swings, rather than a larger playground that contains swings as one of many features.

playground:swing=yes has the benefit of allowing more feature tags to be added without resorting to multiple values on one key (like playground=swing;slide) which is usually good only as a last resort.

Hope that makes sense. Thanks again and happy mapping!