You do not add your son's W-2s to your return. Unless the W-2s amount to $6300, he is not required to file a return unless he wants to claim any Federal or state taxes paid.
https://www.irs.gov/publications/p501/ar02.html#en_US_2016_publink1000220702
Filing requirements for dependents
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Your unearned income was more than $1,050.
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Your earned income was more than $6,300.
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Your gross income was more than the larger of—
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$1,050, or
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Your earned income (up to $5,950) plus $350.
