A 4-month-old previously healthy infant presents to the emergency department in January with 2 days of coryza, cough, and increasing work of breathing. He has poor feeding but is producing wet nappies. Vitals: T 37.6°C, RR 54/min, SpO₂ 93% on room air. Examination reveals diffuse crackles and wheeze, moderate chest wall indrawing, and no focal consolidation. According to the Canadian Paediatric Society bronchiolitis guideline, what is the most appropriate initial management?