They should not seize your 2019 refund for student loan debt.
You should be aware---in the future, if you owe student loan debt, child support or back taxes, if your refund is being seized for your debt, it will not matter what the refund is for--they will seize all of it up to the amount you owe, whether any part of the refund is based on child-related credits or not.
If you claim a child as a dependent, that will probably give you a tax credit and increase your refund. So yes it is subject to seizure if you have a debt offset. There is really no way to separate "your part" of your tax return from dependent's "part" of the refund. You are one taxpayer with certain income, deductions and credits and it all goes in the same blender.
However, if your dependent has income and files a tax return, your dependent's tax refund is never taken for your debt; and a child who files a tax return can still be your dependent if they meet the usual requirements.