Opportunities for children to be physically active during the COVID-19 pandemic were limited, resulting in a decrease in overall physical activity and an increase in sedentary behaviour during the lockdown restrictions of the pandemic. This study further explored these changes across various stages of the restrictions, starting during the first UK-wide lockdown in March 2020 through to the “new normal” in December 2021. Nine families, consisting of eleven children (36% girls, 64% boys; aged 13.38 years ± 1.14), eight mothers and one father were tracked throughout this time, using semi-structured interviews to explore the fluctuations in physical activity and sedentary behaviour in the home environment in the context of self-determination theory. Findings indicate that as restrictions eased, physical activity within the home decreased, as children were exposed to more opportunities at school and in the community; these opportunities seemingly increased children’s motivation to be physically active through increasing levels of their basic psychological needs of autonomy, competence, and relatedness. Some children’s physical activity levels have returned to pre-COVID-19 levels, with a newfound enjoyment for being physically active. Whilst others now prefer to pursue more sedentary behaviours that became habitual during the lockdown restrictions. Accessible opportunities now need to be promoted to drive up children’s motivations to be physically active following the years of uncertainty around the COVID-19 pandemic.