You misunderstand. My children have had chickenpox and they even played several times with a (vaccinated) friend who had whooping cough (pertussis). The chickenpox was no big deal -- just a rash and fever. And they only got the mildest of coughs from whooping cough while their vaccinated friend had a bad case of whooping cough that needed medical attention. I would not have even known that it was whooping cough if their friend had not been diagnosed.
I myself am 48 years old and so I had measles, mumps and rubella as a child, and I can tell you that none of my childhood friends or relatives were injured from those either. It would not worry me at all if my children were exposed to those.