D7 for family members

Good day

I have a question about a D7 application with family members. I have different opinions - some say that the D7 is given only to the main applicant, and then after getting the card, you apply for the family reunification; some say you can apply for D7 visas for everyone at once.

We are going to apply from South Africa and are meeting the income requirement for the whole family. I would like to know how embassies usually issue the D7 visas since the reunification process can take a very long time, and we would like to go all together (practically not possible to leave children back home).

Thank you.