Human-computer interaction (HCI) research has recently become more interested in studying practices. Looking beyond the novelty of technology, practice studies try to understand how technology becomes integrated into everyday life and how it shapes everyday practices in the longer time span. The contribution of this article is to demonstrate how ubiquitous computing practices develop. The article also sheds light on children’s and their families’ smart device practices in private and public settings. This paper responds to the recent call for practice studies in HCI and tries to understand technology-mediated practices of children and their families in their everyday lives. We first focused on children’s practices with a multipurpose public display through an ethnographic field study, and then broadened our focus to the children’s and families’ smart device practices through a diary study. We showed that children’s practices with a public display were surprisingly similar to their other information and communication technology (ICT) practices at home and elsewhere. In both settings, displays were used for entertainment and time-killing, as well as for babysitting and social interaction. This study indicates that technology-mediated practices do not spring up from the ground fully formed. There are several factors contributing to the practices’ emergence: the artefact itself and its affordances, the nature of the space, and the mind-set of the users. This finding has many implications for research and design, indicating that when developing technology, we should pay attention to a variety of factors that might be contributing to the emergence of practice around that technology – factors not yet fully explored by current research.