A dependent child will be required to file a return for 2005 if their gross taxable income exceeds the greater of $800 or $250 plus their earned income up to a maximum of $5,000 (i.e. a maximum standard deduction of $5,250). If a childs earned income is less then the filing requirement they may still want to file in order to receive a refund of any income tax withheld.
If a child is under the age of 14 (as of 12/31/05) their unearned investment income in excess of $800 is taxed at their parents top marginal tax rate. The parents may elect to report their childs unearned income on their tax return by filing form 8814, Parents Election to Report Child Interest and Dividends (http://www.irs.gov/pub/irs-pdf/f8814.pdf), thus precluding a filing on behalf of the child if the unearned income is their only income.
For 2006 the standard deduction increases to $5,150 and the excess unearned income rules now apply to dependent children under the age of 18.
So, unless your son had Federal income tax withheld, he is not required to file an income tax return since his gross earnings for the year of $2,500 are less then the threshhold of $5,250.
Because it is impossible for me to identify and consider ALL the relevant facts, this advice is not intended or written to be used for the purpose of avoiding penalties, and cannot be used for that purpose.
Yes, the 1040EZ would be most appropriate. I assume he had federal income tax withheld that you want to get refunded.