Would it be possible to buy a $99 flight on my Amex Plat, cancel it for a frontier credit, then buy a $198 flight using the credit and another $99 charge? And repeat to use up say ~$500 in Amex credits across different cards? So in the end I'll have Frontier credit associated with a cancelled reservation for ~$500 that I could apply toward a family trip costing say $700?

It seems like this would work but my concern is whether a $500 Frontier credit from a cancelled reservation booked in my name only could be used by me to book 5x$140 tickets for $700 in the names of me and my 4 other family members. Will that part work or such a $500 credit would only work for my own $140 ticket and not for the other tickets in the reservation due to different names?