My first concern is there is an addiction involved however children will be with their dad 50% of the time?? That doesn't make sense. Even someone seemingly the best parent with an addiction until that was addressed I would be concerned having the child exposed that much. Anyway, another topic I am sure and I didn't get a feel for what you were directing as far as what addiction!! I would however have him leave and remind him that he needs to seek help for himself. They need their home and they need more of a 20/80 split right now if their is addiction involved. 50/50 when they are in school is VERY hard on kids. I see that the kids I watch here at home. They need one main consistent environment and visiting dad on weekends provides just that. They need to be at the same place as often as possible.
So, I am a single mom, two kids 4 and 7. My ex moved out of state and we divorced when they were 1 and 4. It wasn't easy. I can tell you from my mistakes, be honest, to the point they can handle. Do it together, stand united in your parenting at all times. Make sure they understand the loss of the marriage is not the loss of their parents in their lives. Explaining that sometimes problems are so big that they cannot be figured out. That space and time sometimes can help it. That you both will be there for them and that you will do whatever you can to keep life as they know it. Never bad mouth the other and they don't need the explanations of the addiction in the mix right now either. That is something as they get older you will need to address. Consider a good play therapist for the kids too, to work through what they are going to feel and learn to communicate feelings.
Kids are amazing. They are resilient but at all times they need to feel secure, protected and as much of their daily routine needs to remain the same as much as possible.
I would say 50/50 shared custody can create tension for them too as they never feel really stable somewhere. I am not sure why you are leaving the family home, not the father if he has the problem with addiction. Just because you want the relationship to end doesn't mean you have to leave. I think having dad involved in their lives is essential, however they need a strong sense of stabliity. Bouncing back and forth doesn't always create that as much as just seeing dad every other weekend. It is hard to say as I am not in your shoes, I am on parenting duty 24/7.
I just protected my kids too much. I didn't want them to see me cry or worry. I wish I had talked to them more. Of course my son was way too young but with my daughter I made mistakes. She created her own worries and felt uncomfortable talking about it as she grew. I took my daughter to a play therapist as she had some residual behavior problems from the changes and we learned a great deal there. It opened up a whole new way of parenting for me and helped us both to learn to trust and talk to one another. Answer any and all questions directly with them. Be conscious of their age however be honest to what they can manage to handle.
I am all for if it is time to let the relationship to go and you have exhausted every possible way to fix it, then ultimately it is best for your kids. Kids need stress free living, they need parents happy and if you show them you are okay, then they will be too, promise. Kids just need happy parents and if divorcing is the only way then they will adjust. It takes time, there will be behavior changes to watch for but if they have a consistent routine and you are open with them it is easier on them. Let them know they can come to you anytime with anything. Let them know you love them and that will never change. Keep the same schedules for them at both homes. HUGS, God bless you on your journey and peace be with you! :)