In this paper, we describe three studies for the design of a hand-held music device for children. The studies involved researchers from different disciplines and children from different schools. We reflected on what happened during the design activities. And we looked at the outputs produced by the children in order to understand the feasibility of the activities that were included in the design sessions from two perspectives: whether they contributed to the design of the product – termed their capability – and whether they suitably involved children in the process – called their suitability . We then report on how children’s ideas were selected and integrated into the product design through iterative cycles of testing and refinements. This description of the process prompted the discussion on the involvement of children and their ideas throughout the whole process, its benefit and difficulties that could be applicable to a wide variety of design contexts with children.