What did Father want to do about the newchild?
The first answer does not say anything wrong, but I wonder if you are not asking about what Father wants to do with Gabe late in the book.
At that point (it's p 164 in my copy, Chapter 21), Father wants to release Gabe. As the first answer says, he had brought Gabe home to try to get him to be less fussy. But it hadn't worked. Gabe had been given to a family on a trial and he cried all night. So even Father has voted to release him.
When Jonas finds out that father wants to do that, he takes Gabe with him when he leaves.
So my answer would be that Father wants to release Gabe, the newchild.
I am not sure which new child you are talking about. I recall the two newborn babies that were in the nursery. The father had weighed them and then determined which one was smaller. He talked to the baby and then put a shot into the fontal which killed it. He then put it in a box and disposed of it.
The one child Gabriel was having trouble sleeping nights and would have to be released. Father asked if he could bring the baby to his home so he could try and get him to sleep through the night.