It is possible for family member ( wife & son ) to apply for DTV together with my same application ?
Or they should wait till I obtain mine and them apply themselves?
TLDR : Answer Summary
Yes, family members, such as your wife and son, can apply for the Digital Visa (DTV) together with your application. However, if applying online, they may need to submit a copy of your DTV application. The feasibility of joint applications might vary depending on whether the consulate supports online applications or requires in-person submissions.
DTV VISA RESOURCES / SERVICES