Need some advice about sick cousin

So I just found out my sons cousin has rsv and a double ear infection. The problem is that my fiancé and I are getting married next Friday (dec 15) and it’s his brothers child that is sick. His brother and sister in law are both in the wedding. The wedding rehearsal is on Wednesday (dec13) so they will be coming to stay with us starting that day. What advice do y’all have as far as me trying not to let my 4 month old child get sick. I don’t want to tell her not to bring her son because he is exclusively breast fed but at the same time I don’t want to have a sick baby for my wedding or honeymoon. Any advice?