Actually, this is probably the best way to go (what mistoffolees said). Delaying this kind of action would only allow the situation to exist longer than necessary.
But I would also try to extend an olive branch where you could, to find out why he felt he should quit his job. He obviously did something to himself in addition to the children, unless he's working under the table somewhere.
Also, out of curiosity, are you working? Sometimes an obligor will hold resentment if he (or she) is the only one supporting the children financially, especially if he feels that he's supporting two housholds exclusively. This can cause him to reach a point of exasperation that would make him want to sort of eject from feeling trapped. (I'm playing devil's advocate here. These are the kinds of things that will come up in hearings, and it's probably useful to consider what happened from his perspective beforehand.)
Plus, if you understand his perspective on the matter and try to find middle ground where you can, it will work out over the long haul. Desperate people do desperate things; and when they're desperate enough, a finger-wagging Judge Judy type at the family courthouse can toss out as many orders as she wants.