Just think of your OWN life... is there really an "ideal" time for you to hear news? I've been waiting for my life to "slow down" for the past 20 years! Life doesn't slow down... it keeps going. So, I'm pretty sure your ex won't really ever been in the "right state" to hear what he needs to --mainly, that you are putting your kids first (instead of him) and need to do what's good for you and your kids.
i'm sorry for guilt feelings. I think most of the time guilt can be alleviated by just stating your intentions--coz we get scared that what we're feeling or thinking or about to do or did already do is something "wrong"... but im sure you already know that whatever you choose to do is obviously being chosen to do with the best of intentions--so whatever you decide, there's no need to feel guilty... we're humans, and more importantly, we're the ones that were the "healthy" side of the relationship and we're allowed to make up our own decisions!
guilt is probably just the residual emotional reaction you subconciously remember in dealing with decision-making with an alcoholic in your life.