As a kid this was my least favorite vacation but as an adult it was one of my favorite. It is 2,000 miles and to do it right you should take 7 - 10 days. Both times I took this trip we went thru Spokane, WA, as a kid Silverwood was not yet built so as you can imagine this trip is almost all scenic and with the exception of Yellowstone where there are quite a few kid things to do it really is for adults...just my view. With kids I would reverse the loop and end at Silverwood for a few days. -- Jeff Richford
Mukilteo To Silverwood
The drive from Mukilteo to Silverwood is approximately 6 hours. Silverwood is a really fun park with not only a water park area, but also rides, restaurants, and lots of other kid friendly attractions. Allow at least two to three days at Silverwood.
Silverwood To Yellowstone
From Silverwood to Yellowstone is one of the most scenic drives in the US. There are rivers, lakes, mountains, trees and desert... sa beautiful drive.