Originally Posted by Cymro

Yes; you might have an issue if, e.g., one of you has status that enables you to check in at a check-in desk for a higher class of travel than you're actually booked in, but you can still meet up at the lounge (assuming that there are enough higher status passengers to guest everyone in).

I think fast track security is for everyone on the booking but I'm not sure; again, no guesting if not on the boarding pass and the higher status passenger isn't present.

But fundamentally, the contract is for carriage and you don't all have to present yourselves at the same time.