A 4-month-old boy presents to the emergency department in winter with a 2-day history of coryza, cough and increasing work of breathing. He has subcostal recession, respiratory rate 56 breaths/min, oxygen saturation 93% on room air and widespread crackles and wheeze. Feeding is slightly reduced but he is still having wet nappies. According to Australasian bronchiolitis guidelines, which management strategy is most appropriate?