Do I just pretend their earnings are the parents', or is there a separate way to enter kids' info?
Do not enter it under the parent.
A separate tax return must be filed for children who have unearned income that is greater than $11,000 or any amount of earned income. If a child's unearned income is less than $11,000 and greater than $1,100, the child's unearned income can be included on their parent's income tax return.
For the tax year 2021, the Kiddie Tax applies if your child has unearned income (usually from investments) exceeding $2,200, is required to file a return, isn’t filing jointly, and was age:
From <https://ttlc.intuit.com/community/income/help/what-is-the-kiddie-tax/00/25913>
Open or continue your return if you don't already have it open.
If the child's unearned income is less the $1,150, there is no need to file a return or claim it on your return. The FAQ below should be able to assist you in determining when and/or if, a child needs to file or you need to include their income on your return.
Where can I enter the Foreign Tax paid on Child unearned income to bring up on Foreign Tax Credit claim?
Q. Where can I enter the Foreign Tax paid on Child unearned income to bring up on Foreign Tax Credit claim?
A. You can't do that if you file the child's income on your tax return (form 8814).
You will have to file a separate return for the child or forego claiming the foreign tax credit on your own return.