Be careful about thinking about it in those terms. Bomb or not, she will do what she's going to do with it, despite whatever your expectations may be.
It may be more helpful to think of it in terms of making a life-affirming decision for yourself and making a decision and change to better your situation. I say this because you're right...a divorce is going to be messy and expensive and, frankly, painful. But if you're focused on improving your life and living according to your new design for living, you can leave all the baggage in the right place and move through it gracefully. It will also keep you open to whatever reconciliation might be possible if the alcoholic changes and makes it possible. "Dropping the bomb" mindset tends to burn a lot of bridges.