I thought I knew all the needed info, but now realize maybe not...so asking more seasoned You

I have a group of 6 me included. I am AY plat and others are cattle. I am considering spending my 60000 worthy points for upgrading all to finish the LHR-HEL trip, but I wonder about fast track and lounge.
I could obviously take only 1 guest as emerald to CX first lounge and fast track so if I upgrade all to business, does that allow fast-track at LHR T3 for my friends as statusless J pax, and can they also use the CX business lounge (if not, then where does AY send J pax?) which I guess is the best of oneworld T3 business lounges.
Flying AY metal (not A350 unfortunately) FWIW