An owner and his wife work in a small business and their two children work part time and never have become eligible for the 401-k Plan. Should they (the children) be included in the ADP and ACP testing as contributing 0%??

I think you meant to include this post in the 401k thread, not the 409A one.

Anyway, if they children never became eligible for the 401k plan, they should not be included in the ADP/ACP testing as contributing 0%. If they did become eligible to make elective deferrals before the plan year being tested ended, and those children did not make any elective deferrals, then you should include them as 0% in the testing.

Thank You!