Sick 9 year old stepson

Hey ladies. We are going to have my 9 year old step son on Christmas for a few hours and he was sick this past week. He had a fever and nasty cold. You could tell by just looking at him. My son is 4 months old and I realllly don't want to risk him getting sick. My husband wants him to hold him and love on him on Christmas since he only seems him MAYBE once a week but I'm nervous. Would you let him hold the baby? And my husband gets reallllllly mad and defensive when I say anything about his 9 year old. I know if I tell him I don't think it's a good idea he will FLIP.