This is what it looks like:
The crew will comprise the voucher holder, his/her two guests, and the instructor pilot
The aircraft captain (voucher holder) selects origin and destination airports, controls the aircraft for takeoff, flight, and landing, monitors all systems (assisted by instructor pilot).
The two guests place themselves in the two seats behind the pilots, watch the crew at work. They may take pictures and/or video and swap seats with the ship commander.
The instructor pilot is responsible for pre-flight briefing and helps the trainee at all flight stages and in emergencies, explains the intricacies of the aircraft’s functioning.