If your kids are getting a tax benefit from earned income, that earned income probably has to be reported to the IRS in a Schedule C. My dad has my sister keep track of her babysitting money throughout the year (doesn't have to be fancy, just a notepad with dates and amounts and the family she babysat for) and file a tax return. She's under the threshold of owing anything, but that way everything is reported and then you can use that the filed Schedule C as the "earned income" support for the Roth IRA.