Great trip report and glad to see you traveling with your son. I did the same with mine on JL First as a baby and a toddler and the service was fantastic.

As a baby, JL gave us all of row 2 with 2 businessmen and a former NY baseball player from Japan in row 1 (who spent a few minutes baby-talking with the baby)! The second time as a toddler, they gave us the 4 seats on the left side of the F cabin with only one other person in 1K. The flight attendants were fantastic and brought toys and they also had backup baby bottles and diapers as a baby.

For meals, he loves rice and soup; he also likes eggs so it worked out well. We ordered kids meals for him as well but they let him sample different items on the menu. I think the passengers were all relieved that he slept throughout most of the flight (as was I so I could enjoy the flight). He was also a pacifier baby/toddler so that was a great way to make sure he was quiet.

All in all, we've taken him on some of the longest commercial flights since we go to Asia pretty often; he does much better in J and F because he can comfortably sleep but Y tends to be a nightmare...