The best parks for kids in London include Diana Memorial Playground in Kensington Gardens (pirate ship playground), Coram's Fields (adults only admitted with a child), Queen Elizabeth Olympic Park (three playgrounds and splash pads), Holland Park (zip wire and Japanese garden), and Victoria Park in East London (two playgrounds and a boating lake).
The best playgrounds in London are Diana Memorial Playground (Peter Pan themed with pirate ship), Tumbling Bay in the Olympic Park (sand and water play), Holland Park Adventure Playground (zip wire), Battersea Park Adventure Playground (den building), and the Hampstead Heath playground with summer paddling pool.
Yes, all London parks and their playgrounds are completely free to visit, including the Royal Parks (Hyde Park, Richmond Park, Greenwich Park, Regent's Park, St James's Park) and council-run parks across every borough.
Parks with splash pads and water play include Queen Elizabeth Olympic Park (Tumbling Bay water play), Granary Square at King's Cross (1,080 fountain jets), Princess Diana Memorial Fountain in Hyde Park, and several council parks with seasonal paddling pools including Brockwell Park, Hampstead Heath, and Victoria Park.