Just don’t do it if you can help it. If you are traveling internationally with kids, don’t choose a route via the US which will require a border crossing. Trust us. Even if you just pop through the States en route back to Canada, you will probably be subjected to a multi-hour wait in one of their hubs, where children, babies and visibly pregnant women are made to wait in a Homeland Security immigration line with hundreds of other able-bodied adults. No water, no chairs, no assistance. I became so irate after my 1 and 3 year old were at risk for dehydration, diaper rash was setting in, and our rancid yogurts were the only grub around (security confiscated my ice packs) that I had to cause a stink. Even when I made up a story about being pregnant and faint, they still wouldn’t usher us any closer to the front of the line. Moral of the story: have someone in your group sprain their ankle before you pass through the USA, and tell your airline you need special assistance. The wheelchair and special treatment you and your children will receive? Priceless.
Other tips and requirements: www.dhs.gov