One person can take everyone's admission cards to the fast pass machine.
The number of fast passes will depend on how you work the system. Your fast pass will have a one hour return time window. You will be able to get another fast pass at the start time of the return time window or in two hours (whichever time comes first).
For example if your fast pass return time is 1:10 - 2:10, you will be able to get another fast pass at 1:10. If you used the FP machine at 9:30 (meaning the return time is longer than two hours away) you will be able to FP another ride at 11:30.