Accompanying 16YO for in person appointment

I am currently in the US on H1B, along with two dependents on H4 (all through change of status).
We are traveling to India to get our H visas stamped, but are facing an situation to which we can’t find a clear answer even after talking to the Visa support center.

Situation: My spouse and I are eligible for dropbox, but our child is not (since he was less than 14yo when he got his last visa). My son is 16yo now. Currently, my spouse and I have a dropbox appointment, while our son has an in-person appointment (2 weeks after parents’ dropbox appointment). We have tried called the support center to see if we can all go together for an in-person appointment, but have been advised against it. So, the parents will go for dropbox, and the child will go for in-person interview.

Questions:

  1. Can parents accompany a 16yo for visa interview; the support center tells me anyone above 14yo will need to go in alone? I don’t think that’s reasonable for a teenager. In some places, I read a parent can accompany a minor under 18yo.
  2. Do parents need their passports to accompany the child, or would US driving license be sufficient as ID? I am worried about a situation where parents’ passports are still in processing / transit, when child’s interview is scheduled. We have kept 2 weeks gap. If parent’s passport / visas are not required, we would like to get child’s appointment completed asap so we can travel back earlier.

Can someone please share their experience on either of the two questions? Thanks in advance!