Whilst I appreciate that QFF points is in the title, the author did mention that they had 320,000 AmEx membership rewards points they could use which I think transfers over at a 2:1 rate to Singapore Air meaning they would have 160,000 SilverKris miles and could technically make the booking for 4 passengers using those points. All I'm doing is merely pointing out this option should QFF not materialize which based on the discussion thus far seems to be the case (yes there is availability out of Denver but this would require the OP to transport themselves and their colleagues to DEN and deal with all the logistics there versus a direct trip to LGW from DFW).