My name isXXXXX a licensed attorney. Glad to try and help out.
Sure sorry for the circumstances, truly. My heart goes out to you.
I can only imagine what you must be feeling right now, so I'm pleased to share the following information with you. Either of you can file as long as one (not required to be both of you) meet the California residency requirements of residing in the state for the past six months or longer and the county of filing for three months or more. There are literally hundreds of different factors to be considered, but the two "biggies" are parenting and property. When it comes to parenting, custody will be decided pursuant to a legal standard called what is "in the best interest of the children". For property, yours is a community property jurisdiction, meaning the presumption is an equal or 50-50 split, which is generally a favorable position.
Without a single doubt, there is one thing you can do right now that would be the most helpful. That means speaking with a local family law attorney without delay. In other words, please don't wait to see if and when your husband files. Rather, seek legal counsel now and without telling your husband ahead of time. To help folks in this online venue, I am required to follow site rules including refraining from accepting cases and/or making direct referrals to named attorneys. However, I can tell you where I would turn were I in your very shoes. Toward that end, my very next step would be to take advantage of the resources of the non-profit, American Bar Association accredited, National Board of Trial Advocacy Division of the National Board of Legal Specialty Certification.
Here is a listing of all such Board Certified Family Law Advocates practicing in your jurisdiction (please just click the following link):
This database, which is also officially endorsed by the State Bar of California, can be searched by geographic locale, as well.
With children and military service being in the picture, I would absolutely urge you to not proceed as a pro per (self-represented) litigant. However, should you do so, I also wanted to share what is (in my opinion) the very best free resource for such help:
Judicial Council of California / Administrative Office of the Courts
If you have a follow-up question or need clarification, please just say the word by using "reply" to reach me.
I truly hope all works out for you.