If you're going through Oregon on I-84, you can't miss Multnomah Falls as it's right along the highway. I found my best shot was from the parking lot in the median of the highway because I was far enough back to get a good angle on the falls. The wreck of the Peter Iredale (Warrenton, OR) can be interesting if you're there early in the morning before too many people are there.
Cross the Megler Bridge and stop at Cape Disappointment in Washington. Go to Waikiki Beach if the waves are good (or even if they're not that great) and visit the Visitor Center and Lighthouse.
If your workshop doesn't stop in the Hoh rainforest then go there yourself. Same for many of the beaches like First Beach and Rialto Beach. Take a hike to Sol Duc Falls. It will take 20 minutes or so but it's not a hard hike and doesn't have much elevation change.
If you're in Port Angeles drive through the Mckinley Paper Company and out to Ediz Hook to shoot driftwood. It's piled up along the side of the road and there is plenty of room to park.
Be ready to stop or make a U-turn at any moment anywhere on your trip because photo ops will pop up as you drive. It's a great area so have a great time! Bring plenty of memory cards!