The child tax credit rules for 2021 tax returns were unique to tax year 2021; you could receive the CTC even if you did not have any income earned from working.
That will not be the case for tax year 2022. For tax year 2022, the rules revert back to the requirement to have income earned from working in order to receive the refundable part of the CTC. If you do not have at least $2500 of income from working you will not get the CTC or the additional child tax credit. And the age cutoff went back to under 17 (not 18).
And...without income earned from working you are not eligible for any other child-related credits like earned income credit or the childcare credit.
If you get Social Security benefits with your kids ssn you do not enter it on your return. It would only go on their return if they have other income to report. Otherwise nobody reports it,