Rehabilitation after childhood lower limb loss is complex and dependent on multiple stakeholders and environmental factors. While research with adults underscores the importance of involving prosthetic limb users and caregivers in discussions to drive innovation, children are often excluded or not effectively engaged. This protocol lays out the development and implementation protocol for an internationally applicable research toolkit which has been designed and evaluated around the essential presence of the child. Research domains span their unique prosthetic needs, quality of life, pain, and mobility. Cohorts of children in contrasting environments were identified (Cambodia, Gaza Strip, and the UK) to provide a comprehensive global understanding of the child with lower limb loss. A literature review revealed a lack of appropriate tools for identifying paediatric prosthetic user requirements leading to the development of novel interview guides for each key stakeholder: child, caregiver, and prosthetist. The child's guide centred around enjoyment and engagement using card games and activities. A panel of experts in paediatric limb loss and mental health rigorously reviewed the guides. Guides were integrated with existing validated measures for quality of life, pain, and mobility to form a comprehensive toolkit. The toolkit was successfully piloted with 5 children, their families, and 2 prosthetists. This protocol lays out the toolkit rationale and implementation plan (Jan 2023 to Dec 2025). This work offers the opportunity for this cohort to enjoyably engage with research that seeks to radically improve prospects for all children living with limb loss. The outlined best practices ensure ethical considerations when working with vulnerable cohorts. This study is approved to cover implementation at all geographical locations as well as the researcher institutions. Results will be disseminated through national and international conferences, as well as through manuscripts in leading peer-reviewed journals.