I have taken Mrs NM plus three Mini- NM's plus Mrs NM parents (so 4 adults + three munchkins) into QF, BA, and AA lounges based on my WP status and Mrs NM's QC partner membership. BA at LHR T1 would not allow all 7, but were happy to permit the 5 NM's into the lounge.

Similarly, AY and CX allowed access for me, Mrs NM and 3 Mini-NM's and for them, Mrs NM's QC membersip does not count. The only lounge that requested guest passes was the QP at HKG.

AA permits any accomanying family members access to the AC's.

In all cases except AKL, we were asked to use the J lounge rather than the F lounge that I would otherwise have been entitled to use. This was partly a space issue (we had a party of 7) and partly that they wanted to keep the F lounge kid-free. We were happy to oblige.

So it depends a bit on who the guest is. If related, then should not be a problem for AA. If kids, then they allow some extra flexibility. Otherwise it depends on the desk agent and how busy they are on the day.

In Totonto, the BA desk agent asked that if the lounge got busy, would we please leave before she had to ask us to do so. We agree and kept close watch. But we only occupied 4 seats that had been arrange in a cluster and the kids were happy to sit on the floor between us. It didn't get so busy that we felt we should vacate the four chairs we were occupying.