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.