Through a set of participatory design (PD) sessions with children with visual impairments and their educators, we understood current practices in maths teaching, and designed a novel system to support learning for this particular educational context. Sixteen children were engaged in 19 PD sessions to develop tangibles and auditory stimuli to represent numbers, and to explore activities to use through a tangible user interface. We describe the context and lessons learned along the PD process with children and educators, and their implications on the design. Two main outputs were derived: iCETA, a multimodal tangible user interface that allows the use of tangible blocks to represent numbers; and, Logarín, an audiogame designed for iCETA that enables mathematical training. We explored the use of iCETA and Logarín during 15 sessions with 11 children with visual impairments. Results indicate that playing Logarín is engaging and capable of promoting their mathematical abilities. This research supports evidence that PD is successful in bringing children and other stakeholders together to design a solution that fits children’s needs and promises educational impact.