Holidays and sick cousins 😷

So it seems a tradition for my husbands sisters to bring their sick kids to family gatherings. The first time it was hand foot and mouth. Now as Christmas is rapidly approaching one of them has pink eye, fever and throwing up. I feel like they should stay home instead of possibly infecting 5 other children including a newborn. Why is it that I am always the bad guys for not wanting my kids exposed to illnesses and choosing to stay home. If your kid is sick stay home! Am I overreacting?