Seattle > North Cascades National Park > Seattle > Olympic National Park > Seattle
Day 1 - Home > Seattle > North Cascades NP
Stays:
Day 2 - North Cascades NP
Day 3 - North Cascades NP
Day 4 - North Cascades NP > Seattle
Consider adding 1 day to spend in Seattle. If you want to skip Seattle, take this Ferry as a shortcut to Olympic NP
Day 5 - Seattle > Olympic NP
Day 6 - Olympic NP
Day 7 - Olympic NP > Seattle
Day 8 - Seattle > Home
Also consider doing a portion off the Olympic discovery trail (biking) in Olympic National park.
Reference Links:
https://www.thewanderingqueen.com/pacific-northwest-road-trip-itinerary/
North Cascades National Park:
https://www.readysetpto.com/your-guide-to-an-epic-north-cascades-camping-trip/
https://www.earthtrekkers.com/north-cascades-national-park/
Other Hikes:
https://www.earthtrekkers.com/best-hikes-in-north-cascades-national-park/