You mentioned that you "did not work." The child-related credits are based on income earned by working, so you cannot file a tax return and expect to receive earned income credit, child tax credit, additional child tax credit, or childcare credit if you did not work.
If you had other sources of income like Social Security, investment income, rental income, retirement income, etc. you MIGHT need to file a tax return.
Who has to file?
http://www.irs.gov/uac/Do-I-Need-to-File-a-Tax-Return%3F
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