Thanks to the couple posters with the garden grocer suggestion - I think that may be one of our best options since we'll probably need milk, snacks, and some other things too. We'll have laundry available to us so we can afford to pack fewer clothes and instead of just a backpack that doubles as a diaper bag we'll probably bring another backpack so we'll be able to help disperse the load that way. We're going for 9 days and if I pack 4-5 diapers a day it ends up being enough that for us it could be the difference between checking another bag or not. Also when I said I wanted to 'at least put a pack of diapers' in the bag that is all I would ever think of doing.

It is what we did the last time we took our car seat and it just helps it from getting dirty and the latch belts from getting broken.

Just to clarify a couple of things - we would be checking the car seat in a nylon bag made for car seats. Hi everyone - OP here! Thanks for all the honest and respectful responses, I truly appreciate everyone's input. The worse thing they can do is take the diapers out and you'll have to take a cab to the store and buy some. I'm guessing your situation is a little different from ours, since we just do it for convenience and for hands free traveling. Since we could all bring a carryon, we could carry the stuff on board, but we prefer to not carry on anything. We've never given it a second thought and we surely don't hide it as we stand there before getting into line and start packing it up. Pretty much whatever we don't want to carry on the plane. There are mugs and toys and jackets, maybe a fanny pack or 2. Often it's the 2 yo's car seat, with the 4 yo's boster seat - both in one store bought bag-black w/zipper. I can't tell you the stuff we throw in there. for Jetblue, we check them at the counter when we get there. We generally check our bags with RAC, but the carseat(s) can't be checked until we get to the airport. When not in use, compact bag folds easily into the integrated drawstring pouch. This standout bag is a handy travel accessory large enough to fit most umbrella strollers. We don't do it to avoid the fees, we just do it at the last minute. Make checking a child's car seat at the airport a breeze with the Prince Lionheart car seat gate checkBAG. since the granddaughters share a suitcase, and are allowed one bag each). Keep in mind it was before all of the baggage fees and we fly Jetblue so each of us get a bag allowance and often never use it all (esp. OP, we have loaded our carseat bags a few times and it's never been a problem.

Car seat check bag