Assistive technologies (ATs) must improve activities but also the participation of impaired users. Thus when designing ATs one should consider the diversity of users and disabilities but also the educational and societal contexts, as well as their subjectivities (i.e. personal experience of disability, own motivations, etc.). Co-design is a method that encompasses all those aspects, but it is not easy to achieve with impaired users, especially when they are children. In the context of a research project on interactive maps for visually impaired people, we first conducted a field study to better describe potential users (visually impaired people, but also parents, teachers, therapists, etc.) and their needs. Building upon this fieldstudy, we developed a set of design cards representing users but also needs, places, goals, etc. We then designed a workshop aiming to improve researchers' empathy and knowledge about users in ideation step of the design process. We report on how these methods facilitated the creation of inventive scenarios, interactions and prototypes, but also how they helped researchers to reflect on their own design and research practices.