H4 dependent Drop box for wife and son

I have valid visa stamp, and my wife’s visa stamp has expired and she is eligible for drop box.
But I have son who does not have prior visa stamp.
Can my wife and son together go for drop box? or First I need to get visa stamp for my wife and then get separate appointment for my son

They can both go for dropbox at the same time. Also physical presence of your son is not required for drop box, you wife can drop on his behalf.