A Cough, A Sneeze

So when is a cough just a cough and a sneeze just a sneeze and nothing more? 
When is it safe to take the little cough-er out in public?
Is it bad to go outside on a somewhat warm day when they have a runny nose?
When do you worry and when do you not?
How do you not worry when they don't want to eat or drink and thus they only have 2 wet diapers in a 12 hour stretch?

Oh the things on my mind as my little ones are sick.