You may want to consider asking the court to preemptively order her not to interfere with your custodial rights.
The contempt proceeding merely seeks punishment for non-compliance; you'd rather actually spend the time with the children.
Since the email is her "notice" to you of her refusal ask the court to make specific orders for the transportation of the children here to California, with date/time etc. That way, if she refuses to obey that order you have a stronger case for the contempt. The ultimate "punishment" for the failure to obey the court's orders, and interfering with your custody rights, may be to change custody, but you have to get that request to the court.
I suggest you search AVVO for a local family law attorney, or contact the L.A. County Bar Association for a referral to a family law specialist.
yeah just add a supplemental declaration adding the new counts.
This is just my opinion and not a comprehensive answer. You assume the risk because this answer may not apply to your situation depending on the facts.
Sign up to receive a 3-part series of useful information and advice about child custody law.