All I can say about Florence in late July and early August is HOT!!! I am often asked the best time to visit and I think mid-March to mid-June, and September through mid-November. If you want to visit when there are fewer tourists, March, April, October, November are best.
I have just spent some time in Whistler, British Columbia and loved it! Beautiful waterfalls to hike around and great restaurants too. Chia had a wonderful time!
The shopping was underwhelming, but the scenery was spectacular.
It is a long 5 hour drive from Seattle to Whistler. I recommend driving to Vancouver, B.C. where you can do some fun shopping, spend the night, and then go to Whistler. The Pan Pacific Hotel was fabulous and welcomes pets, too!