So the three took their first plane ride over Thanksgiving. H and I were rather nervous about making the cross-country trek. I solicited advice and packed a large carry-on with little games, puzzles, and snacks. I thought I was over-packing, but I think it turned out to be about enough stuff.
They did well and we got several compliments on their behavior. Our only issue was pottying. We had some turbulence on the way to California so the seatbelt sign stayed illuminated for a good portion of the flight. H had words with a flight attendant and passenger over getting up to take them to the restroom. But that was really our only problem. When we returned home, we limited their beverages so we didn't have to get up as much, but also the seatbelt light was not on very much.
H and I are not jumping up and down to get all five of us on a plane again anytime soon, but overall we feel it went well and will go even better next time.