Do I get approved for the DTV visa and then add my wife and son or do they apply at the same time?
TLDR : Answer Summary
You typically need to receive approval for your DTV visa first. After approval, you can reference your DTV visa number to apply for your wife and son as dependants. At walk-up consulates, all applications can be submitted simultaneously, whereas with eVisa online applications, you need to wait for your DTV approval before applying for your family's visas.
DTV VISA RESOURCES / SERVICES