My DD is kissed by her key worker every morning. DD will go and give everyone a cuddle to say hello. I feel pleased she's so happy there and so well cared for and then I bolt for the door to enjoy my quiet morning
What a shame you can't see your DS is being looked after by a caring person.
If you were uncomfortable you should have taken hold of your DC and said "That's enough kisses for now."
I can't beleive you dind't do that.
To write a letter of complaint afterwards is just odd. You will greatly upset your child's key worker, who will be left wondering how much affection to bestow on your child, and my actually withdraw totally. Is that what you want from your child's key worker? Personally I think a quiet word with the key worker and the manager would be the best way to go. She may think you are a bit paranoid about germs, but while you have a good relationship she will probably respect your wishes.