The participation of end users in design, research and evaluation has long been a feature of HCI. Traditionally these end users consent to participate in the general belief that they are contributing some knowledge that will eventually improve things for themselves or others. The involvement of children in research in HCI creates new challenges for ethical participation. This paper brings together current research on ethical participation and models of participation, and presents three tools, CHECk, ActiveInfo and PICO- Art, as well as a set of practical ideas, for researchers to adapt and use in their work with children. The paper explores how effective different aspects of the different tools are, and offers a set of practical suggestions based on observational assessments. The main contribution is a culturally adaptable ethical toolkit and a protocol for ethical working with children in HCI.