The practice-based research project “Move the Neighbourhood! - with Children” is themed around children’s use of public space and developed and constructed through a collaborative design process. Through co-designing, building and assessing a public site in a local community, the aim is to examine if and how co-designing urban sites in collaboration with children and a related stakeholder network, can contribute to better locally integrated playful outdoor-spaces. We are exploring if the process has an impact on the neighbourhood in two ways: through the actual on site intervention development with the children, as well as on the local planning process. In this paper, we present the setup and discuss the role of the co-design project as a site-defining place-making strategy in relation to these two perspectives, based on the projects first steps of negotiations and interactions. We address the children’s engagement with and understanding of the site, as well as the role of the project seen in the light of emerging development plans for the area, thus discussing the notion of ‘impact’ in relation to spatial design, participation and decision-making.