This article presents the design process of Iromec, a modular robot companion tailored towards engaging in social exchanges with children with different disabilities with the aim to empower them to discover a wide rage of play styles from solitary to social and cooperative play. In particular this paper describes the design process from the elicitation of user requirements related to three main target users - Autistic children, Moderate Mentally Retarded children and Severe Motor Impaired children - to the robot design, highlighting problems and challenges encountered to meet and reconcile heterogeneous needs of disabled children. Modularity and configurability are the key features of the robot: the use of plug&play application modules, the coating components and add-on elements contribute to the flexibility of the system in creating rewarding games that can be easily understood by the child and can promote fun and learning. Other key features of the system are the combination of autonomous and usercontrolled behaviour and a strong emphasis on identity and expressiveness that can be dynamically adapted during play. A main contribution of this work is that it does not just focus on the engineering aspects of robotic design, but it is primarily guided by learning and therapeutic issues and centred on the final user.