I assume the EIN is for the child. It goes on the child's return and you indicate that the child is claimed as a dependent. The child may owe some tax, based on the AMT. of the UTMA. 

How do you report the UTMA in the child’s social security number. It’s under $300. 

If that is their only income the child does not have to file.

Otherwise report it on the child's return.