Really FT needs a resident agony aunt for all these things. Someone to answer all the awkward social questions - should I tell my friends, should I wear a tie in first class, should I bring chocs for the CC, are white trousers a good idea on BA etc etc.
But to answer the OP - who cares? Is it really such a big deal that you are separated from your friends for 7 hours on an overnight flight? Surely you know the answer to that. Why not just tell them, as if it they find out some other way one could be left looking a bit silly.