If you have one person in your party that has a GAD voucher but may not go to the parks can you use that persons voucher for FP for everyone else that is going?
The person whose name is on the voucher must be physically present at the Park Ticket Window with a photo ID and a valid multi-day pass. Once the Fastpass Exchange Cards are issued there is nothing to prevent that person from leaving (and even giving their Exchange Card to someone else).