A 2-yr-old boy is seen for his routine check-up, 4 weeks after an episode of bilateral acute otitis media that resolved uneventfully with antibiotic treatment. He seems generally well, but his mother reports that he is not hearing as well as usual. On pneumatic otoscopy, both his eardrums appear amber, opaque, and retracted, and both are immobile. Otherwise his ENT examination is unremarkable. Which of the following treatment regimens is the most appropriate to institute at this time?