How do you approach telling family your rules for baby?

Here in the US it is starting to get cold outside which means people are going to begin getting sick... my little guy just turned a month old and I want to do anything I can to prevent him becoming ill. A Facebook acquaintance just had to hospitalize her baby because he has whooping cough... so I am terrified. This evening my LO and I will be at a Halloween party filled with family and friends that will want to hold him. I was hoping to discuss my rules of washing your hands (which they should already know since I have been saying it since he was born) and not kissing the baby anywhere (my mother in law tries to get around this rule but once again they should know since I have repeated it since birth)... my big issue is that my husband’s grandmother is losing her mind. I was blessed to know her before she started to fade but she is now to the point that she can’t remember conversations from an hour earlier and honestly can’t be left unsupervised. She always wants to hold the baby... which when she does we have to watch her like a hawk... but she kisses him... on the head and his hands. She also wiped her nose with her hand and continued touching him the last time she saw him. I get so anxious when she is around because I honestly don’t want her holding him but I don’t know how to politely say it. And it isn’t like she would remember me discussing it later in the evening. Any suggestions on how to go about it? I thought about baby wearing but then no one gets to hold him which that may be the only safe way to go about it... Any advice is appreciated!

Edit: Thank you all for responding to my post! I shot out a text to all of our parents to let them know we are changing our “Rules” about handling baby. They were all made aware that we are going to be strict and only our parents were allowed to hold him but with stipulations attached. My parents were very supportive and called me right away to let me know they are very happy with my decision. My mother in law responded coldly with just “OK”. Talked to my husband and he told me she has to get over it and he is fully backing me. Thank you again!