Is guesting one into each lounge a legitimately allowed? As this might be a solution if the F lounge staff are not feeling accommodating. If if it is of slightly questionable legitimacy can I still try it if we get rejected asking nicely for the 3 of us to come in at the F lounge (ie am I likely to get caught out for poor behavior and rejected twice and so would it be better to just guest one to J and one to F from the start)
Not that I've had experience in guesting into the International lounges, but I would've thought the approach would be:
1. Rock up to F Lounge first and politely request if possible to guest both in
2. If that fails, walk away, draw straws for who's going to J lounge.
3. Go with 1 guest only to J Lounge and take in as guest.
4. Hang around for short period and then discreetly leave J Lounge, leaving 1 guest there
5. Collect other guest and head to F Lounge to enter legitimately. If F Lounge query where other person is (that is, if their questioning seems to indicate some concern about what you've been up to), distract somehow to avoid providing a proper answer... "poor friend drew short straw and had to stay at Maccas..."
Surely your friends would be appreciate the opportunity to be guested into any lounge at all regardless which one they each end up in? Of course, one may just get a slightly worse deal, though no worse than not having a lounge at all, some may say. Good luck.