I'm no expert, since I left my XAH when my DD was 15 months old...but I also had to leave behind my 12 year old stepson and it broke my heart. Your children may not like you for a while and they may not understand your choice, but you are the adult in this situation (the SOBER adult) and it is your responsibility to look out for their well-being. While your AH is busy diving head first into a bottle, he may very well endanger your children or other people on the road while he's driving drunk. In addition, you have a right to live a happy, HEALTHY life without a toxic partner dragging you down.
All this to say: be honest and tell your children as much as they are able to ask about. Your 11 and 9 year olds may have more questions, but your 6 year old may be satisfied with "Daddy is sick right now and can't live with us".
IMO, you are letting your fear of being "the bad guy" keep you in a toxic marriage where your partner knows full well you won't follow through on enforcing your boundaries.
And let's be clear here: what's happening right now is a direct consequence of your AH's choice to drink. If anyone's the bad guy here, it's him.