vestibular dysfunction post temporal lobe injury

Hi there,
I am a physiotherapist who provide home rehab to patient victims of car accidents. I normally get them started at home and then transfer them to outpatient clinics once they are mobile.
I have this case at this time; a 3.5 years old boy who was struck by a boulder to the temporal lobe while in the backseat of a car. Glascow coma scale of 3/15 at scene. Has overall recovered remarkably physically but will show signs of dizziness/loosing his balance when looking up. He is able to run at this time, look sideways and back when walking/running (although we try not to run). There are numerous behavioral issues which makes it very difficult to treat conventionnally. I have brought the boy to a nearby park, going down slides, climbing, will however not go on swings. We have played catch, played soccer, basketball. He refuses to imitate me, does not want to walk on a plank. I have told mom to try to get him to do front flips on the bed (obviously) to try and stimulate his vestibular system. This little boy lives 1.5 hour away from a big town therefore resources are limited. Although I have treated clients with head injuries before, i am not a pediatric physio and who specializes in neurology. My goal is to bring him to a local pool to do some rehab there. Any thoughts on what else I could do to improve his balance???? Julie