Stop kissing babies on the lips!

Since my son was a baby, I’ve had a few people kiss my now toddler on the lips. My husband and I have never been OK with anyone else kissing him on the lips because of the spread of illness (especially now during covid) and honestly because we just don’t like it - it’s very personal. I’ve tried to casually mention just hugs or kissing on the cheek only but now that we’re about to welcome a newborn also, I realize that I really need to establish boundaries around this to prevent the spread of illness.

Am I overreacting? Can anyone provide guidance on how to go about establishing boundaries around this without it blowing up? I am mostly concerned about my MIL telling me I’m overreacting 😒