Nope - you'd need two Golds to get the three of you into GF: you can always ask, but I doubt the lounge agent would ever allow you in....you'd have to settle for Galleries / Club lounge otherwise...
One of the minor annoyances of BAEC - I travel for work on pricey tickets, which gets me to Gold. I hardly ever guest anyone into the lounge on those trips. I occasionally go and guest Mrs Ratpus on our holidays...but the once or twice a year we travel with friends (or I travel with friends alone) there's no lounge access...
Would be nice to get a mulligan on some extra guests maybe once or twice a year, rolling over all those times I guest no-one - but that will never happen!
Bad luck, I'm afraid.