I second the suggestion for wegoshop.com or garderngrocer.com

Both are VERY conveinent. I have used both. Our first trip we used wegoshop.com , nice but I had to go to
WalMart and write down everything I wanted to buy, the quantity, price, etc...
Our second trip we used gardengrocer.com, they have a website that has everything you need and you actually can shop online on their website. It's awesome!!Only costs $12 to deliver, definitely worth it. I am doing gardengrocer.com again for this trip, and I would recommend them to anyone who is flying (especially if you have small children- carrying all those diapers, wipes, snacks, etc. can really weight a bag down)
Good luck!!! Have a great trip!!