Long outpatient waiting times pose a significant global challenge in healthcare, impacting children and families with implications for health outcomes. This paper presents the eHealth system called eADVICE (electronic Advice and Diagnosis Via the Internet following Computerised Evaluation) that is designed to address waiting list challenges for paediatricians. Initially designed for children’s incontinence, the system’s success in terms of health goals and user experience led to its adaptation for paediatric sleep problems. This paper focuses on user experiences and the development of a working alliance with the virtual doctor, alongside health outcomes based on a randomised controlled trial (N = 239) for incontinence. When reengineering eADVICE to sleep disorders, the promising results regarding the reciprocal relationship between user experience and building a working alliance encouraged a focus on the further development of the embodied conversational agent (ECA) component. This involved tailoring the ECA discussion to patient cognition (i.e., beliefs and goals) to further improve engagement and outcomes. The proposed eADVICE framework facilitates adaptation across paediatric conditions, offering a scalable model to enhance access and self-efficacy during care delays.