I have several family members arriving at CDG. I will already be in Paris. Rather than them each having to deal with getting a Navigo découverte when they arrive, can I get them in advance?
That is, I would go in advance to a ratp/métro ticket booth that sells them, armed with my family's photos. I'd put each one's photo on a pass, along with their name. The passes would be ready to charge up when they arrive.
There's no reason why you couldn't purchase more than one Navigo Découverte in a single transaction, although an individual ticket agent may balk at draining their supply of card blanks.
If you explain that it is for your family members arriving shortly, I would hope the ticket agent is understanding.
Failing that you could always go to multiple different ticket agents and get one Navigo Découverte from each.