Children is the plural for Child. Child’s is the singular possessive form of Child. Children’s is the plural possessive form of children.
We use children when we want to make the word “child” plural.
So it is:
I have one Child.
I have two children.
Child’s is the singular possessive form of child. We use the possessive form of child when we want to show that one child owns something.
This is my child’s friend.
I need to look after my child’s cat.
Remember we are talking about only one child. You can replace “child’s” with a name if that makes it easier to understand.
This is Jane’s friend.
We need to look after Jane’s cat.
Children’s is the plural possessive form of children. Because the noun doesn’t end in “s” and we want to make the word possessive, we need to put the apostrophe before the “s”.
This is our children’s house.
In this case, many(more than one) of our children live in the house and they own the house together.
Childrens’ is incorrect and should not be used in English. We don’t put the apostrophe after the “s” because “children” is an irregular plural and does not end in “s”.
“Childs’” is incorrect because the plural of “child” is “children”.
Children’s or Childrens’ Menu/Meal
“Children’s Menu” is correct because you are usually aiming your menu at more than one kid so therefore you should use the plural possessive.