Elite Plus Companions
 

My family and I are traveling Y on AF from CDG-FCO. There are 6 of us on the PNR and 2 of those are Elite + through DL. Will the other 4 be able to also use Priority check-in, security and boarding?

I would definitely use the elite+ checkin with one of the elite+ members going to the counter first and asking if it is OK to checkin the whole group while not everybody beeing elite+. 99% sure they will process you as a group there.

As with priority security I would also ask but would deem your chances there a bit lower. Same with boarding later on.

You have nothing to loose to try, but do not take it as granted for sure.

In my experience, travelling with one E+ and the rest of the family, priority check-in and boarding is not a problem. Security highly depends on the airport you're travelling through, especially at outstations. With KLM at AMS or CSA at PRG, it's never been an issue, however, KLM/AF from CPH is a no-go, as the handling company only gets paid for the one E+ passanger and strictly enforces the rules.

Priority luggage tags is hit and miss. Sometimes they put them on all suitcases, sometimes they spend extra care to only put them on the E+ passangers suitcase, even asking which suitcase belongs to whom, though we're clearly travelling as a family and will have to wait for the final suitcase to arrive anyway.

In any case, it can't hurt to ask, in a lot of cases, you'll be lucky.