Government policies recommend, and all stakeholders benefit, when mental health services meaningfully engage with carers and family. However, health service engagement with carers is inadequate, and often non-existent with children whose parents are service users. There are seven fundamental ways that carers and families want to be integrated with and engaged by health services but current survey instruments do not capture these seven engagement practices. This protocol describes the development of two closely aligned Family and Carer Surveys (FACS) to measure engagement of service users in mental health services. The new measures are based on the seven engagement themes and a conceptual distinction between the carer and family, with particular focus on where the service user is a parent. The instruments will be developed in five stages; (1) item generation (2) Cognitive pretesting of survey (3) preliminary item content quantitative assessment (4) psychometric analysis of a large data collection and (5) selection of items for short form instruments. These steps will operationalise the seven fundamental ways that families and carers want to be engaged with mental health services, thereby providing valid and reliable measures for use in research and benchmarking of carer and family engagement.