Well here's the thing about waiting for the alcoholic to be sober, short of him detoxing for a long period of time say 30 days or more. Your still trying to talk to a alcohol saturated brain, just because he hasn't consumed alcohol at the moment doesn't mean he's any where near sober.
At some point in time the nicey nice coddling of the alcoholic must take a back seat to the well being of your children and possible other children.
The importance of the issue lies with the importance you give it. Right now it appears excuses are taking center stage. You need to ask yourself WHY is it so important to speak this boundary to him nicely rather then just set it for yourself. Often in the early stages of learning about boundary we get confused on if they are for us and our peace of mind or little manipulations in hopes they will stop drinking and see the light.