You did right to call the police.
When I found out for 100% sure that my AH had a problem it was such a shock, even though I had had suspicions for such a long time. I felt kicked in the stomach and numb. I went through our life together retroactively with my new eyes and so many things suddenly made sense and I realized my former memories were not reality. And then there is the future. Now it was going to be different that what I had anticipated, whether I stayed or left. And I was angry, at him for bringing this to our marriage, at me for missing the now obvious signs.
Just breathe and let this all digest and take advantage of the support of your parents and his parents. You don't have to make any decisions, big or small immediately, or even this week (other than the driving and child minding ones you have already made - and good for you on them).
Get comfortable and read and read and I sought out Alanon. It is for family and friends and it is a good source of support from people who have been there and done that. At first I would think "what am I doing here?". They recommend that you go to 6 meetings at a couple of different groups before you decide if it is for you. It took me all 6 meetings to realize how helpful it would be.
Please know you did not cause this, you cannot cure it and you cannot control it. It is his to deal with. And please know that it is rare that the alcoholic can find sobriety and recovery (2 different things) on the very first try. Although he may honestly believe it when he is telling you he is quitting it for good, he may not be prepared for how truly difficult it is and he will probably lie about it if/when he relapses.
And please don't think "if he loved me/us...." If love could cure this, there would be no reason for this Site! It is full of people who loved their alcoholics.
Keep reading and posting and be extra nice to yourself and your kids.
This is not for sissies, but you've already shown you've got what it takes to get through this.
p.s You haven't failed your kids, but yes, things are different now. You'll manage fine as long as you keep them foremost in your plans.