Not what you asked, but make sure:
1. The contributions to the child's IRA don't exceed their earned income.
2. They file and pay any self employment taxes required. See "Who must file?" in the Form 1040 instructions, especially Chart C item 3 regarding earnings from self employment exceeding $400.
Also not what you asked, but they can withdraw their contributions from their Roth any time without penalty. Earnings must remain until 59.5, else generally subject to taxes and early withdrawal penalty.
My kids put theirs in Schwab SWTSX, but it's money for the long haul, not for college.