Just eyeballing your routes it appears you will be missing Glacier NP on the trip west and Yellowstone NP on the trip east.
For Portland, you could bend over to the mouth of the Columbia River (Astoria, OR) from Longview/Kelso, a drive that parallels the river. It is worthwhile driving the coast at least as far south as Lincoln City, OR, and then move on to Portland. There are some state and private campgrounds along the coast. Ecoloa State Park (near Cannon Beach) and Oswald State Park (Short Sands) are worth visiting and hiking. Short walk down from Short Sands parking area down to a beautiful pocket cove through old growth forest. The beach towns are nice as well.