A 6-year-old boy from a slum in Delhi presents with his mother complaining of eye discharge and mild redness for 2 weeks. On examination, he has follicles on the upper tarsal conjunctiva and mild conjunctival inflammation. Giemsa staining of conjunctival scrapings shows intracytoplasmic inclusion bodies. His mother reports that two younger siblings also have similar symptoms. What is the most appropriate immediate management?