What does the vet say? I realize they are 16 and some cats live much longer than that.
Since blood work came back normal and BOTH cats are doing this........Maybe they are adjusting to your baby in the house and this is their way of getting attention. They have been "replaced" in their minds by the baby who is rightly so getting more attention right now, therefore acting out.
I am typically not a crate trainer but in this case, crate training might be a good idea OR keep them separated somehow.
We have always had dogs and fortunately didn't have those issues when daughter came along.
My daughter did rescue a cat about 6 months old which was set to be euthanized at the shelter for social issues. She didn't respond to anyone who tried to take her and she is a beautiful tortoise shell and weighs 4# but her hair makes her look bigger. Anyway, my daughter didn't find the available cats receptive to her and she asked about this one. It was like they found each other.. even the attendants could not believe the instant bond.. this cat went directly to daughter's lap, sleeps with her and is actually a cat/dog. Great cat. She kept her strictly in the bathroom and slowly allowed opened up the rest of the condo to her so she would not be confused. It is the best thing daughter ever did!
That said, maybe you cold adopt your cats out if you can't control the behavior. I would seek out some behavior specialist before I euthanized 2 normal cats with no health issues who had the world as they know it turned upside down by a new baby. Hopefully they can adjust to the new routines and schedules with more attention from you.
I agree that your child should not be in any contact with litter, pee and poo from cats. I hope you find a solution that works for your family.