Although drug use interferes with effective parenting, it rarely indicates the user is a danger to others. Unless their history includes violence, I wouldn't eliminate the possibility of visits completely.

I would set firm boundaries to be sure. Let them know you are happy to meet them someplace like the playground or whatever you have in your area, but you expect them to be clean and sober for these visits. If they go well, then perhaps you can expand that to more face to face contact with visits in their home, or the grandmas home or after some time your home. Their caseworker may have even more ideas for you about supervised visits.

Worst case scenario, their actual behavior at these meetings is unacceptable and you revise things. I wouldn't draw a line in the sand now based on what might happen, though.

DS's first dad has a drinking problem (probably drugs as well), and has had several DUIs/car wrecks in the last three years and even went to jail for a few months. He is hurting himself, and the people that love him, but is not a danger to us or DS, as he is not violent, and has been sober when we visit.

This first mom probably does not think she is a risk to the baby. Tell her honestly why you are scared to have face-to-face contact. Many people who are involved with drugs do not realize that they are a danger to others around them. If you are friends with the first grandma talk to her about her daughter. My idea is if you are comfortable with the first grandma and sister why not have the first mom only visit if she is with them also. Maybe it would put some accountablity in for the first mom if her mom and sister always had to be with her during every visit. Since you are more comfortable with them. By the way,if you are going to send pictures and updates make sure you can follow through on that. My experience is that I was promised updates and never even got one. Being a first mom is very very hard. You have to remember that birth/first mom have a very very very low opinion of themselves. Thats why some of them engage in risky behavior, because they see themselves as worthless. If she thinks you don't like her she might think you couldn't possibly love her baby. Try and think about the postive things about this first mom. Sounds like she needs alot of help in her life. I really hope her family or friends are there for her.

How do you feel about openness with firm boundaries? Could you all sit down with the case worker and talk about possibilities? Perhaps a concrete schedule on neutral territory? (At a restaurant, at a mall, at grandma's house) What kind of follow through will you have if whatever plan you have doesn't end up feeling safe?