If the child's only income is interest and dividends, it can sometimes be reported on a parent's tax return. If the child has any other kind of income, then all their income (including interest and dividends) must be reported on their own return.
However, even if the child's only income is interest and dividends, and if the amount is less than $2300, then the child will pay no tax if the child reports it on their own return, but the parent probably would pay tax. If the amount is more than $2300, you may need to speak with a tax advisor or prepare some test returns to see which way is best to report it.
https://www.irs.gov/taxtopics/tc553
