Childhood cancer survivors adjust to the physical, mental, and social difficulties associated with their illness and treatment. This process can be facilitated by social support from peers. For children, this is often problematic due to geographical, clinical, and age-related limitations. This paper reports on a stakeholder assessment study that confirms the relevance of a digital peer support service for childhood cancer survivors. The analysis establishes where in the existing health care process the digital peer support service should be introduced, what actors play a key role in facilitating service onboarding and use, and characterizes desirable user experience qualities. The analysis also yields a collection of design challenges to be addressed in the development of the digital peer support service.