each tgv car is numbered at the door, and each seat is numbered. the upcoming stop and time until you reach it is announced on the train, but it’s a good idea to know the stop ahead of yours, especially if significant luggage, children, or agility is involved.
on your return trip to charles de gaulle airport, be sure to confirm which station your train leaves from, as some of the cities have more than one. give yourself some time, especially when traveling with children and luggage; sometimes the main stations are vast, with trains leaving on widely separated tracks, or, in smaller stations, from platforms requiring the negotiation of stairways.
once aboard, if your luggage is too large to fit overhead, you can store it in the common space located in each car of the train (just be sure to keep an eye on it at the stops along the way). then settle in with a glass of wine and a fresh baguette and watch the beautiful countryside roll by as you’re whisked away to your destination.