In this chapter, the authors consider a researcher's perspective in projects involving design of assistive technologies for and with children who have moderate to severe limitations, such as cognitive impairments, impulse control issues, strongly reduced vision, or speech problems. The secondary objective is to introduce the concept of vulnerability in such complex design contexts, exploring it in relation to researchers, the user group, and other stakeholders. They argue that awareness of diverse risks can lead to a design process that reduces or even eliminates some of these risks, empowering both researchers and users in the process. The case used as a basis for discussion is that of an iPad app design for and with children in a special education class, and later, with children in occupational therapy.