There is limited evidence on diet and physical activity (PA) interventions to prevent childhood over- and under-nutrition in Nigeria, particularly those with parental involvement. The aim of this qualitative cross-sectional study was to explore parents’, children’s, and other stakeholders’ views on what might enable or hinder participation in diet and PA interventions with parental involvement, and potential intervention components likely to be feasible and acceptable. The study took place in Lagos State, Nigeria. Sixteen boys and girls aged 8–11 years in four participating schools were involved in the study. In addition, women (n = 19) and men (n = 13) aged 18–60 years took part. These included parents, teachers, school heads, community leaders, health professionals, and health or education civil servants, recruited via the participating schools, community and professional links. Data were collected in schools, homes, and places of work via one-to-one interviews and focus groups, audio-recorded with participants’ consent. Topics included knowledge about a balanced diet and active living; frequency of exercise and barriers and facilitators of participation; and ideas for fostering good diet and physical activity habits. Socio-demographic data were collected orally at the start of each discussion. Thematic analysis of verbatim transcripts of the recordings was conducted. Three overarching themes were identified: (1) Active community collaboration; (2) strategies for involving families; and (3) schools as key settings for interventions. The main barriers to participation in potential interventions included poor access to clean water, safe outdoor play space, and menstrual hygiene products. Suggested solutions included increased security, infrastructure improvements using recycled materials, school gardening, and health campaigns funded by local dignitaries. Health literacy education for parents, tailored to local dialects, was considered an important potential intervention component that would engage families. The feasibility and acceptability of grassroots suggestions for intervention components and parental involvement could usefully be explored in future pilot studies.