Double edged sword for etiquette here.
While you should not leave your freinds, your friends should not prevent you!
You could try a couple of things:
a) all arrive at the F lounge, see if you can get entry for all. If you can't, then you ALL go to the QF club together. This is a fair outcome (along the lines of - 'oh well we tried'). Now at this point your friends SHOULD say 'well you go in we'll meet you in an hour' - that would be the proper etiquette on their behalf.
b) all arrive together and check-in. then as you are walking through the shops, wait for a moment when the two couples are drifting apart (you know, to look at different items) and say 'hey - let's all meet at the club in one hour' (and you scuttle off to the F lounge - if they call you say you are still shopping)
but i'm not liking B so much...
c) arrive at airport and all check-in. Advise that hubby is meeting business associate in another lounge, and that this is a good opportunity for you (the mrs) to meet business colleague. The two of you go to F lounge and say to your friends 'see you in an hour' etc.