This article explores the relationship between parents’ digital practices and the production of children’s data traces and argues that the multiple variety of data traces that are produced daily about children can be used to profile them as citizen subjects. Drawing on the findings of the Child Data Citizen project, a qualitative and ethnographically informed research which explores the impact of big data on family life, the chapter however deconstructs theories of panopticon surveillance or quantified selves. Instead it sheds light on the fact that the datafication of family life is a complex and messy process, which leads to the production of imprecise, fragmented and inaccurate data. The paper, therefore, argues that we need to start asking critical questions about the relationship between the datafication of children, algorithmic inaccuracies and data justice.