Wow, all 200 of your clients have kids?  But fortunately, there is nothing in the law that prevents you from setting your fees according to how much work you do.  Is your time worth $150 an hour?  Then $25 for that ten minutes.  Of course, there is nothing to prevent your competitors from doing it for free.

There's a website called irs.gov where you can find answers to most questions.  You have to take some time to research, but it took me five minutes to locate the following.  I figure my time is worth $240 an hour, so that's $20 to pass along to all my clients with kids.  I don't have that many because most of them are retired and not supporting their grandkids.  

In January 2022, the IRS will send you Letter 6419 to provide the total amount of advance Child Tax Credit payments that were disbursed to you during 2021. Please keep this letter regarding your advance Child Tax Credit payments with your tax records. You may need to refer to this letter when you file your 2021 tax return during the 2022 tax filing season.

https://www.irs.gov/credits-deductions/2021-child-tax-credit-and-advance-child-tax-credit-payments-t...