After the time is up, the next person stands to be interviewed. Continue until everyone has had a turn. Use a timer to keep yourself on track. It's too easy to get busy doing something and forget to keep accurate time. With younger kids, demonstrate what an interview is, and model the structure with one team while the others watch.
Younger kids enjoy making fake microphones out of rolled up paper or toilet tissue tubes.
They hold the microphone up to their own mouth when they are asking the question. This keeps everyone focused on who is talking. Make sure kids are taking turns in Roundrobin fashion when they are asking questions. Don't let them all yell out their questions because one student will do all the asking. You should see how the kids act when a team member asks the same question as someone else . . .