Unexpired visa when parents are outside US(to show the consular that the child will join the parent(s) who is ready to travel to US or legal status(I94 detail) of the parent(s) is required to prove that child will be joining the parents who is/are already in US.
When a person is inside, visa wont be having higher precedence. Visa is just for boarding a commercial vehicle, not used for anything else.
So expired visa or unexpired visa would be determined only based on where the parents are current located(meaning - if they currently maintain legal status in US or not).
I assume principal applicant is maintaining H status in US - if so then just include I94 copy along with expired visa copy (apart from the documents list they asked in the appointment booking email)- should be enough.