When I separated with a 3 & 6 year old I explained to the children that Mummy & Daddy were having problems being together & that we needed to be apart for now.
The children & I moved houses, I found work & childcare etc.
I am pleased to report that they are now thriving 13 & 10 yr olds.
You can do this.
It is difficult in the beginning & it is difficult being a solo parent but it can be done & the kids can continue to have a healthy life.
It is much better for them to be with you, the responsible parent & have a healthy life than to grow up watching the unreliable alcoholic parent.
Hugs.