You may achive your goals with a debtor exam. I would urge you to speak to a lawyer about filing a motion for contempt. You may find this to more effective and it places the burden on the dad to explain to a court why he is not paying and he can be questioned about his assets in the course of the contempt hearing.
This response is intended to be a general statement of law that should not be relied upon as legal advice and does not create an attorney/client relationship.
Turnover orders work very well in connection with a judgment debtor's exam. That is actually how they are most commonly used.
If the business is simply a "dba" as you imply, there is nothing to actually take. The business and all of its assets are owned by him personally. Therefore, the business is not a separate entity and all of the assets of the business are his personal assets too.
Disclaimer of California Attorney
Although the above response is believed to be accurate, it should not be relied upon as any type of legal advice because the information provided is incomplete. It is intended to educate the reader and a more definite answer should be based on a consultation with a lawyer. No attorney client relation is formed with me without a written contract.
Joshua P. Friedman