FWIW, I can't find where to add the KTN. Google searches turn up conflicting information that you can or can't, where it is to be found or isn't. Yesterday a BA agent told me I needed to speak with the Holidays Team as I booked a package. They were closed and I called back this morning. The agent never heard of this. I hung up and called back. The second agent said there isn't anyplace to add it. He confirmed with a "liaison" there isn't anyplace to add it. I hung up and called back again... got an incorrect recoding that said the offices were closed and try back tomorrow. Pressed redial and have just spoken with an agent that knew exactly what I was talking about. He read back my number and that of my wife's. Apparently I provided them when I booked the flight. It just isn't displayed to the customer. I asked why, and the agent said it was something to do with U.S. Customs and didn't know anything more. I told him how he's the first agent I spoke with that knew what he was talking about - thank you!!

The moral of the story is make sure to provide it at booking, and if you don't see it on the reservation anywhere, keep calling until you get someone that knows what they're talking about. Or just cross your fingers and hope your boarding pass has pre-check printed on it. ;-) At this point I'm optimistic ours will.