No, you should not put the interest and dividends on your return for the custodial accounts set up for your nieces and nephews.
This information is reported to the IRS under the social security numbers of your nieces and nephews, not yours.
Depending on the age of the children and the amount of the interest and dividends, your nieces and nephews may need to file a Tax Return. You can check out this TurboTax article for more details: Filing Requirements for Children.