Virtual and Augmented Reality (VR and AR) are promising to complement practitioners' interventions with autistic children, but they mainly target the socio-emotional abilities of children with low support needs. For autistic children with high support needs, sensory-based and mediation approaches are advised with AR headsets, to keep contact with their familiar environment and their real practitioner, while VR presents risks of isolation. Yet, the acceptability and usability of AR headsets for these children remains unknown. Thus, this paper investigates the possibility to use AR headsets with Magic Bubbles, a multisensory environment designed for autistic children with high support needs, to reassure them while reinforcing the dyadic relationship with their practitioner. Drawing upon a previous design validation with 11 practitioners, acceptability and usability testings were conducted at a day hospital with 10 children with neurodevelopmental disorders and associated intellectual disability. Findings confirm a positive acceptability and usability for these children, thus validating the possibility to use Magic Bubbles with autistic children with high support needs. At last, future directions regarding the use of AR in clinical settings are outlined.