Not to be a debbie downer, but I would try to see if your local Target has these so you can see if they are truly "airtight". Sometimes manuf. use these terms very loosely. I would also wonder on the thickness of the side walls. The advantage of traditional coolers (the ones used for cold/hot items) is that the sides are filled with foam and thus can regulate temps much better. If the sides are thin and not insulated, they would have greater fluctuation of temps. If you can't find them at Target, give Iris a call.
Here is a link to the tote:
http://www.irisusainc.com/p-590-sia-760d.aspx