Thanks for the advice, Legroom.
Our visitors certainly weren't leaving the airport, as they had only an hour from arrival in Brisbane to departure to Cairns. Because they (mother and infant, with three bags and a bunch of baby stuff) were told by Flight Centre that they would have to check in again at Brisbane, we purchased a return fare (CBR-BNE-CBR) for my wife to accompany them and help them through the process at Brisbane. Having discovered that FC had misinformed us, I cancelled my wife's tickets (booked and cancelled online), but of course we're out of pocket for the cancellation fees and as the return leg was with Virgin (which was more convenient time-wise), we now have money sitting in a Travel Bank. Qantas said they would refund the CBR-BNE fare less $88 cancellation fee. Virgin said they would refund to a Travel Bank, less $80. That was on Wednesday. I haven't seen the refunds yet, but I guess it takes a while.
We don't travel often and I should have checked in this forum before accepting the info from FC.
Warwick