When you say doctor gave him all clear do you mean doc said is not contagious? We went to docs nearly four weeks ago both mine coughing doc said coughs can last for weeks and weeks, both still cough a little and have been back to doctors with ear infections, doc checked chest and not concerned with that or coughing, said not likely to still be contagious - so cough could last forever. A little tickly cough in an otherwise well child would not bother me, what with tickly coughs and runny noses you would never get to meet up with anyone. If I were you and he was well but with a little tickly cough, I would prob go ahead with party, but maybe warn anyone with a new born.

I tend to use the would I go to work rule, imagine I have same symptom as kid and if I would stay home from work, then I wouldn't go out etc if I would go to work then carry on as normal.