While some might think the vest is a perfect idea - it seems kinda pointless to me, since the NWA FAs are required by the FAA to prohibit its use during taxi, takeoff, landing, and other times when the seat belt sign is on. During all those times, you will have to discontinue its use and hold your one year old on your lap with only your weak arms.

Ignoring all of the safety concerns with lap children, I recommend buying a seat for your one year old. Do you really wanna hold your child on your lap for that long? I sure wouldn't.

I loved holding my twin daughters when they were little, but not on transpacific flights. That's just crazy, IMO. Do yourself a huge favor and buy a seat for each child. You could then use a car seat if you wish. In my experience, much more comfortable for you and the baby.

Just because you're allowed to bring a baby for 10% of the fare without buying a seat doesn't mean it's a great idea or that you can't buy a seat.