You will need ID for anyone who has a voucher. For kids, this can be an original or copy of a birth certificate.
Disney has stated that GAD FP cards may be limited and may not be available after 11 am, but no one on the DIS has reported being denied, even late into the afternoon during busy times.
Vouchers need to be redeemed at Will Call, which is located outside each park and at the TTC (as well as at MK). You will need to have everyone present with their tickets, and the person whose name is on the voucher has to have a valid multi-day ticket to redeem for the FP cards. You will get a FP card for everyone in your group (up to six people technically, but many have gotten more if they had more in their group).
Have a great trip!