A 18-month-old boy from rural Bihar presents with poor weight gain, developmental delay, and recurrent respiratory infections over 3 months. On examination, he has pallor, glossitis, and angular cheilitis. His mother reports a predominantly rice-based diet with minimal protein and vegetables. Hemoglobin is 9.2 g/dL, and peripheral blood smear shows microcytic hypochromic anemia. What is the most appropriate next step in management?