Short answer: No.
Long answer: You may create an unfunded Trust for your kids at any time, with or without your spouse's knowledge.
Note the word "unfunded".
When a CA resident files for divorce, certain Automatic Temporary Restraining Orders (ATROs) attach, which prevent you from moving assets around (for example, you may not close a joint checking account and transfer the money into your own separate account).
Same goes for the Trust. Creating the unfunded Trust for your kids is permissible, and our firm is occassionally asked to write these; but moving assets into the Trust without your spouse's knowledge would likely violate the ATRO.
In other words, during the divorce you may hire the estate planning attorney and sign the Trust. But wait till the divorce is finalized (or until a judge or your divorce attorney tells you it's okay) before transferring assets to the Trust.
Got more questions? Call us (818.707.8200) to discuss your situation.
[For information only; may NOT be relied upon as legal advice.]