Assessing children's movement competence (MC) offers numerous benefits for academics, practitioners, clinicians and children, allowing individuals to meet children's developmental needs and improve their MC. Yet, there is concern that currently available assessment tools only provide a single plane (fundamental movement skills) perspective of a child's MC. The aim of this study was to elicit the expert opinion of a mixture of academics and practitioners from a variety of fields (research, education, sport, physiotherapy, athletic therapy) to design a tool to measure both the fundamental and functional movement skills of children aged 8–12. A three-round Delphi poll with an international panel of 17 academics (n = 8) and practitioners (n = 9) was conducted. The consensus was that the assessment should assess (a) object manipulation, (b) locomotor, and (c) stability MC and the assessment layout should be dynamic, incorporating a hybrid model of stations and a circuit. Expert consensus was that most skills were to be performed using the dominant and non-dominant side, with object manipulation skills assessed using process and product criteria. The consensus was also that the assessment should have varied ‘layers’ of marking criteria to cater for varying assessor expertise and have a series of ‘add-on” elements to provide a more detailed evaluation should it be needed. These findings present the foundation and content validity of an assessment which takes a dualistic view of children's movement skills, that could be used across several environments (schools, sports clubs, clinical settings, etc.) and could be suitable for use with a large group of children.