GoldenDog....I am glad to hear that you met with a lawyer and seem to be clear on what direction that you want/need to take.
I have a couple of suggestions for your consideration....regarding the kids.
I suggest that they would benefit from the organization "Adult Children of Alcoholics" (and dysfunctional families). They certainly qualify. All kids that have been raised in a home with alcoholism are affected, some way---and, they can carry those affects into their own adult relationships.
At least, you could gift them the literature of that group. You can get their "Big Book" and their other literature in the book section of amazon.com.
You might benefit from reading it yourself....lol.
I agree with you about being careful about not bashing their father. I was careful about that with my childrens' father, after I divorced him (my first husband). I often had to bite my tongue that it is surprising that it didn't bleed. My three children were very small, though.
However, I do think that, especially, since your children are young adults---it is acceptable to make some statements of objective fact without bashing your husband as a person or even throwing blame.
They already know that he is an alcoholic. That is not any news to them. But, the dynamics of alcoholism may not be completely clear to them.
I suggest that it is o.k. to point out to them-----"Alcoholism is very destructive to relationships--all relationships---even to their loved ones. This family is no exception. It has come to the point that separation has become necessary" I am sorry that it has come to this and I understand how hard this change is for all of us."
I think t is good that they are still talking to you. I imagine that they will probably express an amount of anger and pain. I suggest that it is vey important to not try to "make it feel better" for them. I kind of think that it is intuitive for us parents to try to do that. I think it should be resisted to try to sugarcoat anything or tie it up in a nice bow.
There is often a lot of confusion with secrecy and "lies" in alcoholic families---and the kids benefit m ore from the straight forward truth than brushing anything under the rug.
This way they can develop more trust. One of the big dynamics that result from alcoholic homes is that the kids develop a lack of general trust.
(I am not suggesting that every gory personal detail needs to be described).