Well, time ran out and we did not go the box route or the car seat tote bag route. We went the quick and easy route of Glad plastic trash bag.
Hopefully the car seats will not be too roughed up when we arrive...

We voluntarily got bumped, leaving this morning at 9am and have been moved to the front of the plane, recieved 2 $300 TCVs, 2 dinner and 2 breakfast coupons and a stay at a pretty ugly Best Western in DTW. I did not think to ask for an amenities kit, thankfully the hotel had some basic stuff. Only bad thing was I had to go out and buy some more diapers and formula as our luggage went on ahead of us, and we only packed enough kid's stuff for several hours, not overnight.
Oh well, I can't complain Mrs. infinityplusone was game enough to get bumped.