hi hotpeppers-
i find that often the alcoholic assumes we will do nothing and continue to accept the status quo. afterall, we always have, haven't we?
i would definately take steps to safeguard your finances. i certainly wouldn't leave the finances in the hands of a drinker! time to review the finances and see what's actually going on. additionally, if you press her, she might just take off to pursue her drinking with your credit card. you might find that hard to believe but i've seen it time and time again.
consider closing the joint accounts, taking over the finances yourself, and leave her with her own credit cards in her name. an alcoholic will bankrupt you and it sounds as if she is pretty typical in her denial and hiding/lying patterns. i would guess that you haven't even discovered the tip of the iceberg yet.
i think it would be wholly reasonable to explain to her that you have decided that as long as she is drinking, you will manage the money you earn. she'll be surprised, fight against it, and then probably settle into scheming and stealing to maintain her habit.
as for your children, i would take a few steps to safeguard them. they already know what's going on, i would render a guess. if they were my children, i would educate them that if they have seen mom drinking (and kids don't miss much) not to get in a car with them. i would also provide both of them with a mobile pay as you go phone and if any situations arise, they can call you immediately from this phone.
essentially, i would explain that we are a team, we must work together, mom is drinking and explain to them never to get in a car with her if they feel she has been drinking and to call you immediately.
naive