yes, early morning is better, but if you hv to

catch a flight, you would not want to take the chance.

I sure dont want to head out at 6 or 6:30am, just to make sure I can catch the flight at 1pm.

dont forget the drive from border to SEA is about 3 hours. I assume the family has to return the rental car and then catch a shuttle to the airport - and to go thru the security at mid-day ?! Call me being too cautious, I simply wont risk it.