You can't include anyone else's W-2 on your tax return except a spouse. Your child will need to file their own tax return, if required. If they make less than $14,600 with only W-2 income, they aren't required to file a return, but may want to to get a refund if any federal taxes were withheld.
This article may be helpful: At What Income Does a Minor Have to File an Income Tax Return?
