Friend,
"I feel like this is my fault."
That made me cry a bit. (Don't feel bad, a lot of things make me cry right now.)
I fight the "I feel like it's my fault" a lot.
Here's the thing: Just because it makes you feel like something doesn't make it true.
It's just a feeling. It's a feeling of guilt, and it can be there. It can sit there in you and be uncomfortable. Just don't let it blame you. Let it sit there and glare and be all accusatory and sh*t. It'll get tired of it eventually, and it'll be replaced by another feeling.
And maybe, just maybe, that feeling will be -- relief. If you allow it in.
On the surface, right now, you can tell your children "your father is really ill and we won't be seeing him until he gets better." And just keep repeating that. "Your dad loves you, but he's really ill right now and that's why we can't see him."
Deeper down, will your oldest wonder? Sure. But that's a problem for another day. Right now, you just need to handle right now.
And right now may be a lot being a single parent. It might feel overwhelming. But it's not impossible. And there are sides to this arrangement that are good, including that you won't have to worry about whether he's driving drunk with the kids or passing out and not caring for them... AXH is not in our children's life anymore. It's, frankly, easier. And the kids finally have a chance to deal with all the crap he exposed them to.