Dropbox eligibility for H4 Kids below 14 Years

While booking appointment for me and my dependents, it is asking below question

"Do you have a previous U.S. visa in any visa class issued on or after your 14th birthday?"

Dont know what answer to give to this question. My kids are below 14 years old and their previous visa stamped on July 2019 and valid till De 2021. So they have previous US Visa. But it was given before their 14th birthday. In this case, whether my kids are eligible for dropbox.

If not eligible, both the parents needs to be stamped before schedule their interview appointment?

Please suggest the options for my case.

Thank you