Originally Posted by
guineapigjude 
After they're let down, I give the kids the "Dad does the best he can right now" speech and try to explain how he doesn't intend to hurt them, yadda yadda.
Hold up a minute. Is it REALLY the best he can do right now? Or are you "enabling" him by making an excuse for him. I'm wondering if it wouldn't be better to comfort the kids and say "I'm sorry you are hurt." Or ask them how they feel. I think some counseling might be good for them to help them figure out how they feel and how to deal with their feelings.
I'm certainly no shrink. But I don't think you should cover for him. He's making bad choices. The consequences should be his, not deflected by you. Let's face it, unless he changes, your kids are going to struggle with rejection from him. Best to teach them coping skills now rather than allow it to build up over years.