I'm just going to say this:
I was in a similar situation(minus guns and alcohol) 15 years ago. I never got a drug charge, but coke was very much involved. We were just out when the cops showed up. I thought the knock on the door was the person coming back with more. My kids went to foster care. I got charged with two count of child neglect. I got two years of probation. My family has been back together for 14 years. I haven't used any substances since.
This is reality of what Nick is looking at just with CPS (this is what I had to do to reclaim my life):
Random drug screens
Two psychological evaluations
Drug rehab classes(I had 4 hours a day, 5 days a week)
Parenting classes
Domestic violence classes
Seeing children 1 time a week
Stable housing and job for 6 months
6 months of having to open door any and everytime someone on case knocks on door after getting kids home.
Therapy for parents and kids.
These conditions weren't only for CPS. They also were attached to the child neglect charges.
Kayla has options to keep the kids around her throughout this. She proves she is clean and CPS is likely to allow her to live with her parents. She wouldn't be allow to be unsupervised with the kids. I mean if she went to help a child in the bathroom one of the grandparents would have to go in there, too.
The biggest question that determines success is whether Nick and Kayla remembers life off substances. In my experience with everyone who did any of the classes with me, the only ones that were successful was the ones that only had a short drug history. They are doomed if they can't still identify with life before substances.
I believe Nick has a chance. I see the coke as the easier thing to end. The alcohol is so intertwined into his online identity that I don't see how streaming and ending drinking will work.
Nick and Kayla have each other as stumbling blocks. It isn't unusual for one parent to try and the other not to care.
The one thing that is going to give Nick or Kayla no chance is all the talk online. NICK if you are reading this forum STOP! Everyone can say what they want, but you need to seek people who will encourage you. I know you don't feel comfortable with leaning on the church. People will have opinions! Stay in a close-knit group that are supportive of you reclaiming your life. ACCEPT RESPONSIBILITY! I promise CPS is more likely to give your kids back if you accept your fuck up, and straighten up. I seen it constantly people wanting to claim they didn't do anything wrong. Why would they give your kids back if you don't see you did anything wrong? THEY AREN'T!!! Also, DON'T violate the court orders with visitation. I seen more than once children removed from family for allowing visitation against court orders. This is YOUR time to get your shit straight.
I know people might flip out on me, but everyone can kiss my ass. I got my kids, stayed of substances for last 14 years, and have successfully kept my stuff straight.