I am 60 years old getting ready to adopt my Granddaughters newborn ?

I have 3 grown children, 13 grandchildren and this baby wll be my 5th great granddhchild.. The Mother will not be around much at all the rest of us want to be apart of the baby's life. Just how do I go about this and isn't the right thing to do is to have this child call me Mom and later how it became that way. My Son will be God Father and I have other members that will be close to us and there for help if needed. I have so many other questions