Children and youth are increasingly recognized as a stakeholder group that needs to be involved in all planning processes affecting their living environments, such as urban playgrounds. Schoolyards and public playgrounds, as key spaces embedded in the everyday geographies of children, offer a promising site for child-friendly nature-based solutions to counter social and environmental challenges, including health challenges, urban heat stress, and lack of safety for outdoor play. However, greening a city inclusively with children is challenging, and only recently have most European cities begun to explore this. Here, we analyze planning processes for inclusive greening of urban playgrounds and schoolyards in two European cities, Barcelona (Spain) and Utrecht (the Netherlands). Results show inclusive planning with children is challenging due to planning traditions constraining participation, narrow views of non-experts on children's contributions, and a limited understanding of children's agency. In addition, we show that the type of planning affects inclusivity, flexibility, and distributive justice of these playgrounds. Exploring inclusive planning of playgrounds directs our attention to child-friendly urban planning, which goes beyond simply providing playgrounds. It is also about making schools and playgrounds part of the environmental and social transformation of cities and making children part of their planning.