I thought I'd bring up a note from my latest experience as we took DD2 two days ago. Overall, it all went pretty well, but there was one hitch that I hadn't had before in that my card got blocked by the fraud department of my bank. It seems it happened to quite a few people in the queue--since it's charged in US Dollars, banks panic that fraud is happening and block the charge. I had to do a group of phone calls later to get my card reactivated.
Most of the people in the queue that had it happen to them were then able to put through a different card and have it be fine, but I thought I'd bring up that it might be wise to have a second possible means of payment. My husband's business card worked okay after mine was blocked, so I'll pay him back now. They did tell me I would be permitted to leave, get cash, and come back given the circumstances, but the thought of going through the security queue again made my heart ache. I'm glad it worked out okay in the end.