First most likely you are not required to file and from your scenario will not have a need to file.
If social security is your only income even with minimal earned interest then you are not required to file.
As a cursory check take 1/2 of your social security benefit and add to your other gross income (including spouse income for joint filers). If the total is less than $32,000 then none of your social security is taxable. Once you eliminate social security from your gross income, does the rest of your gross income exceed $25,900? If no, then you will not be required to file.
Next, you mention neither you nor your spouse are working so therefore I assume no taxes have been withheld (even from social security). Further, you need earned income to qualify for earned income credits, if you or your spouse is younger than 65.
Finally, even if you filed you should have zero tax owed and the child tax credit is nonrefundable meaning it will be zero with zero taxes owed. Again you need to have earned income to qualify for the refundable Additional Child Tax Credit.
Given no requirement to file, and no taxes to refund or credits to claim you should not file a tax return.
Here is a link to Publication 501. See tables 1, 2 and 3 for more information on who must file and who should file US tax returns.
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