A 4-month-old infant is brought to the emergency department in winter with a 3-day history of coryza, dry cough and increasing work of breathing. On examination, he has tachypnoea, chest wall recession, diffuse crackles and wheeze, and oxygen saturation of 92% on room air. He is feeding less but has adequate wet nappies. According to Australasian bronchiolitis guidelines, which management plan is most appropriate?