Antibiotics are not for viruses, and I'm not a fan of cough medication for babies. Talk to your Dr before you give a baby any medication. A cool-mist humidifier in your sons room during the night is an option or run a shower with hot water for a few minutes and let him breath in the air a bit. Definately keep him hydrated (no acidic juices).
Coughs are usually from viruses, not bacterial infections, so don't give him anti-biotics. You can give him children's cough medicine or call your doctor/talk to a pharmacist for suggestions. Good luck, hope he feels better.