To at least partly answer my questions above, (i) I've bought a pass and have no trouble seeing availability (despite not having a FB account; I am of course logged into my account on the AF website); and (ii) at the flight search stage, the website warns "Please note: Week-End + Pass holders can only add adult passengers.". If I were to try and book fares for my kids "alone" online, the AF system would automatically impose an unaccompanied minor fee. This begs the question of whether I can in fact buy a Carte Weekend+ for each of my kids, and create a booking for them choosing an adult Week-End+ fare.

In any case, the savings are indeed attractive. I searched on fares for Paris-Milan for a random weekend in February, and the R/T fare all-in for a given pair of flights that was €130 for an adult with the Carte Weekend+ would be (i) if booked as a Light fare, €145 for an adult and €120 for a child (2-11); and (ii) if booked as a Standard fare, €205 for an adult and €178 for a child (2-11). And of course the Carte Weekend+ fare is refundable subject to a €20 fee (Standard isn't refundable; and Light isn't even changeable except upon payment of a €100 fee, on top of, of course, any fare change) and, unlike Light, includes a free checked bag. I'd be happy to get my kids a Carte since the cost in this example is only €10 over their Light fare, and comes with the other advantages described above. Perhaps AF is tacitly trying to discourage this, since it would incentivize families to book their holiday travel well in advance.

I've been on hold with AF for 20 minutes to try and clarify ... will report back if I get through before it closes in 13 minutes...