My grandparents will both be there, both almost 90 years old.  My grandfather has MRSA and my grandmother has dimentia.  Neither one should hold my little, especially my grandfather, but they're old school and I know they will both ask - this will be the first time they've seen him in person. I don't feel it's safe. What is a polite way to say no without hurting their feelings?  I won't be wearing a wrap and the rest of the family will most likely have their turns with him. 

Any advice appreciated.