How long does it take to get DTV approval in Thailand, and how should I handle dependants in the application process?

Hello, about to travel from Thailand to Vietnam to apply for my dtv.

Just a few questions. Dtv can take up to 10 days for approval?

If I’m adding my husband and son as dependants, how much time will that add? Do I get approval first for me and then begin the application to add as dependants. Or do I do this simultaneously?

Basically I’m wondering how long of a trip do I need to book, roughly.

Thank you!