Our train arrived at Gare de Lyon and our apartment was close to Gare du Nord. The good news is that there is an RER line (D) that goes from one station to the other with only one intermediate stop. The best news on this part of the trip is that there were escalators that actually worked.
The photo above is me standing in line to get tickets before I realized I couldn't buy the discounted pack of tickets from this machine. I had to go to a staffed window to buy the carnets (group of 10 tickets at a slightly reduced price). The photo below is Niamh pestering a very tired to Muriel.
The photo above is the kids waiting at Gare de Lyon for me to get the tickets. Rowan needed a ticket (half price), but Muriel and Niamh are still free on the metro. The photo below is us waiting next to the track for our train. I thought it was a bit crowded, but my definition of crowded significantly on a later train ride that we had to fight our way off the train before the doors shut.