What would you do?

[Rosey]

I wouldn't think twice about what your inlaws say or think. Your family's health is priority. Give the party a miss.

[dusty]

Avoid the party!

[Jaycee]

Surely if he has a contagious disease they would postpone the party? That would make sense. If not, I wouldn't go and would organise another time to catch up when everybody is healthy again!