Two-week Road Trip From Seattle

[kevin_chn]

Folks,
my wife and I would have two-week holidays from late Sept to early Oct. Coming from Shanghai, we'll arrive and depart at Tacoma, Seattle.

Could you guys suggest some great routes (and spots along them) at this time in year? (Canada included, perhaps)

I'm not familiar with the towns and parks near Seattle and Washington state. I personally have a mileage of roughly 3,000 miles in the US, but most of it was in California.

Another old question would be, is Yosemite accessible and worth visiting this time in year (let's say early Oct)?

Thank you very very much :DD