In this paper, the design process of a tangible game for a tabletop device (NIKVision) is presented. NIKVision is intended to give leisure and fun while reinforcing physical manipulation and co-located gaming for 3-6 year old children. Interaction is provided by the handling of conventional toys and computer augmentation on a table surface. The presence of an additional vertical monitor that complements table surface output is a distinguishing feature of NIKVision. By following a engineering design lifecycle, the paper describes the complete process of designing a Farm Game for the tabletop. Children have been involved, for the very starting point, through continuous test sessions in schools and nurseries. The data recovered from these sessions have been essential, not only to detect problems, but to take the more adequate design decisions. Different children-centred design methods have been used, depending on the question to be evaluated or designed, ranging from observation notes to Wizard of Oz, or video-analysis. The paper exposes the results of a final summative evaluation that summarizes the performance of the game in relation to Usability, User Experience and physical and co-located gaming. The experience obtained by the authors from this process has crystalized in a set of reflections about the feasibility of designing with very young children and about the value of the data obtained from them.