This work is focused on the specific properties and evaluation of full-body interaction design of multi-user mixed reality environments. The main goal is to study how full-body interaction can aid in intervention strategies for children with autism, to improve their understanding and adoption of social behaviors with peers and with society in general. The research is based upon HCI theory, aided by general theories of embodied cognition, embodiment and developmental psychology. The main setting of the research is large scale floor-projected mixed environments, which will allow for testing interaction strategies and evaluation methods of experiences based on collocation of multiple users within a full-body interactive scenario, where they can practice interaction in a natural and uninhibited manner. The research consists of designing playful experiences for the target users in order to promote socialization, collaboration and social inclusion. Topics for analysis include understanding the dynamics of goal-oriented and open-ended gameplay, proxemics, and encouraged group collaboration, on the design of these systems. Assessment methods take into account multimodal analysis, including physiology-based data such as electrodermal activity and heart rate, of the children’s behavioral and affective states in the experience.