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.