These days there are YouTube videos for everything so I would see if there's one where someone documented the same or similar trip. I'm assuming the main reason for concern is changing planes in Paris. I recently did this to get to a hotel at LHR from the Tube station and there was more than one person who videoed the entire thing.

I would definitely print out some main things in English or French, if you can, so they just show them to people and at least have them point them in the right direction.

I would also have them keep their ears open for someone on the plane or departing airport that speaks their language that may be heading the same way or can at least help when they land to offer some guidance.

Lastly, load google translate onto their phone and show them how to use it. 60-65 is not that old and basic communication is much easier than ever.