A 5-year-old child has severe extensor tone and shortened hamstrings secondary to athetoid

A 5-year-old child has severe extensor tone and shortened hamstrings secondary to athetoid cerebral palsy. The child typically pushes into extension when in a seated position in the wheelchair, making it difficult for the parents to position the child for feeding. Which method should the OTR advise the parents to use INITIALLY to stabilize the child in the wheelchair