No face kissing?

So I was reading another post about requiring family to get the TDaP vaccine, which I am totally in favor of but I feel like my parents might... fib. My husband and I also feel very strongly about no one other than Mom/dad kissing the baby on the face early in life, and NO one (Mom/dad included) kissing the baby on the lips regardless of age (his daughter is 7 and we are strictly cheek/forehead kissers). That last one is just a personal decision, not anything we feel strongly about with other people and their kids.

Anyway, my parents should be visiting about 4 weeks after the baby is born and my relationship with them is... uncomfortable at best. I’m sure for those of you ladies who are confident and comfortable telling people to back off, this is a really simple answer, but I have a lot of history with my family that makes me averse to conflict and really uncomfortable with confrontation. So here is my question:

How would you tell your family that kissing the baby on the face is not allowed, knowing that a) they will make a stink about it and b) this will cause my anxiety to flare even more? I have been TRYING to come up with ways to draw boundaries that are both kind and firm so that they don’t feel there is any room for argument.

Anyway thanks for reading!!!