Dropbox for h4 spouse and kid

Hello, I(h4spouse) with my 10 yr old kid, will be applying for visa stamp at india delhi vac. I am eligible for dropbox. Question is whether me and kid can go in single appointment for dropbox? Or i need to get stamped first then my kid in another appointment ? We have valid i797a for both h1b and h4 spouse and kid are which is good for next 3 years. H1b not accompanied with us. His stamp expired but no plans to leave US.

I just replied to this exact question in another thread. Check it.