Holiday in the northwest

Dear users of the US-Car Forum, I ask here because I have found no other subforum. I will fly to the USA with my cousin in June for 14 days. We want to visit Seattle and then also to Vancouver and Yellowstone National Park. Who else has tips, what should not be missed in this area? Mt St Helens, Mt Rainer and Northern Cascades? Mt Rushmore becomes too far. Thank you in advance.