age has nothing to do with if he's ready to be a step-grandfather or not. point is, your son is having a child, your grandchild and your husband shouldnt put rules on how you spend time with your first childchild. he should be happy for you.
my husband and I had our first child when we were not ready (I became pregnant the summer after we graduated high school) my husband's mother and step dad werent too excited at first (my mother in law was just surprised... as was I... but she was excited to become a grandmother), and my husband and his step dad do not have the best relationship. but they are the BEST grandparents to my boys. my oldest will be 5 in April and he LOVES my mother in law and her husband. They had a place for my son to sleep, diapers, wipes, bottles, etc in their house for whenever they had my son.
we moved away from where they live because my husband joined the Navy, but my in laws still have all kinds of things for my boys for when we visit. and my oldest spent 3 weeks with them this past summer (longest 3 weeks of my life though! lol) my mother in law didnt care what her husband thought about having things for the baby in the house, she did it because thats what she wanted. he just gave in because he knew if one of his boys had a baby he would probably want to spend as much time with that baby as he could.
the best advice I can give you is to talk to your husband and stand up for what you want. if you want a crib, you should be able to have a crib. tell him how you feel about it all and I am sure you'll be able to come to an agreement. and chances are, it would be months till the baby spends a full night at your house. (my son was about 8 months old the first time he slept at my in law's house a full night)