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Read the certificates carefully. Can they be used in conjunction with an award redemption ticket, or only in conjunction with a paid (cash) ticket?
I'd be surprised if the terms permit the certificates to be used for travel on any flight other than a US Airways/US Airways Express operated flight.
If there are four in your party, you can buy one (cash) ticket on US, use the certificates for two traveling companions on the same flight, and see if you can get a cheaper FLL-SNA redemption by using your miles on some other flights, operated either by AA or by US.