You should not claim your child's W-2 or self-employment income on your return even if you claim him as a dependent. The dependent would file his/her own tax return and should check the box Someone else can claim me on their tax return in the personal information section.
For more information see below:
https://ttlc.intuit.com/replies/3302077
If you want to file a tax return for someone else, then you will want to create a new TurboTax account because only one tax return can be filed per TurboTax online account.
To create a new TurboTax account, follow the steps below:
https://ttlc.intuit.com/replies/3288574
