The complete details on the pathophysiology of the disease are far from known yet. For instance "The death of a five-year-old boy in New York of inflammatory complications possibly linked to Covid-19 has prompted Andrew Cuomo, the state’s governor, to warn of “an entirely different chapter” of a disease that had been believed to cause only mild symptoms in children."

"Cuomo later tweeted that there have been 73 reported cases in New York of children falling severely ill with a toxic shock-like reaction that displays symptoms similar to Kawasaki disease."

https://www.theguardian.com/world/2020/may/09/children-coron...

In the same hospital?

Their kids likely have grandparents.

I think it's safe to say that most people won't need to be convinced.

The same way you convince them to get a flu or chickenpox vaccine. Most people won't mind, and "most people" is enough for effective containment of diseases less contagious than measles.