I hope this may reassure you. My son and his wife took their seven month old baby on a cruise last year, like yours he had a cough and cold on departure, GP said it was viral and well enough to travel. When they arrived onboard baby was very lethargic and they were very concerned. The doctor onboard saw him straight away, checked him over and prescribed some medication. It cost £100 for this, and they were told they could return again if necessary with no additional charge. They were very happy with the service provided. Thankfully baby perked up within a couple of days, and they had a great holiday. Most people they met were really friendly towards them and the baby.