It has been my experience that when men do this, in this way, it's because they've found someone else.
I was going to say this, too. It's a very familiar pattern.
I cannot stress this enough - document everything, including his phone calls (or lack thereof) to the kids. In addition to an attorney, you may want to look into consulting a forensic accountant, if there is any possibility that he'll attempt to hide income or assets from you or from the court. Your kids are older, so he'll be off the hook in terms of child support in just a few years. Many courts won't consider spousal support (alimony) any more, but since CA is a community property state, you are both entitled to half of whatever the other person has. Your job is to make sure the court knows about all of it, so they can make a fair assessment and division, if it comes to that. He may be perfectly willing to agree to everything you ask for now, and I hope he continues to be easy to work with, but that can sometimes change in a hurry. Make copies now of every legal and financial document you can put your hands on.
I'm so sorry you're going through this...I wouldn't wish it on anyone. Don't forget to use every bit of your support system, and ask for help if you need it.