2 kids ages 10 & 14 earning income mowing lawns

*I Live in Hawaii (for law/tax purposes) This is for year 2023.

Both children (ages 10 & 14) are doing lawn work for family members on weekends.  The 14 year old is mowing the lawn with a non self-propelled push mower, and the 10 year old is raking all the cuttings.   I'm keeping a spreadsheet log of all dates/task/duration/breaks/earnings/whose lawn.   

 

They will not be getting a W2 or a 1099 for the income, as they are being paid in cash by each family member, per job.  Their incomes will be roughly $2400.00 per child, per year.  I want to start investing some of their earnings in a custodial ROTH IRA.  In order for this to be considered "Earned Income", does a tax return NEED to be filed, even if its under $13,850? 

 

Any advice would be appreciated.  Thank you.