A 3-year-old boy is brought to the pediatric clinic by his mother with concerns about delayed speech and social withdrawal. She reports he does not respond to his name, avoids eye contact, and engages in repetitive hand-flapping movements. On examination, he shows restricted interests (spinning objects for prolonged periods) and sensory sensitivities (covers ears at loud sounds). The child has no significant medical or developmental history. What is the most appropriate next step in management?