Mt. Rainier NP is big, and Olympic NP even bigger. To stay in one place at each park to be able to fully experience each park is tough.
Since you are not rv’ing on this trip, for Mt. Rainier I suggest finding a motel in either Packwood or Randle. This is fairly near the Ohanapeecosh Entrance in the S.E. corner of Rainier NP with access to Sunrise, an awesome high elevation viewing area; within a couple miles of the Ohanapeecosh Entrance pull over, park, and take a walk through “The Grove of the Patriarchs”...a beautiful walk through a forest of impressively huge old growth Douglas Firs. Packwood and Randle are somewhat remote on US-12 (White Pass Hwy) so you won’t find fancy accommodations, but the location is perfect in that you are fairly equidistant between Mt. Rainier, Mt. Adams (12,276’), and the backside of Mt. St. Helens. A trip to the summit of White Pass gives you impressive views of the backside of Rainier’s summit. I recommend at least 4-5 days in this location to be able to explore all 3 mountains.
Olympic NP is huge and cannot be seen from one location, but I recommend you rent a motel in Pt. Angeles from where you can visit the NP Visitor Center and Hurricane Ridge, Crescent Lake, and explore the Sol Duc and Elwa Rivers...all on the north perimeter of the Olympic Peninsula. Also Salt Creek Recreation Area near Joyce 12 miles west of Pt. Angeles on WA-112...a beautiful, craggy spot with tide pools, beaches on the Strait of Juan de Fuca. 3-4 days in Pt. Angeles should be enough.
To explore the Hoh Rain Forest on the west perimeter of Olympic NP I recommend you motel it in Forks or google for accommodations in LaPush. Once again this is pretty remote so accommodations will likely be pretty basic. Forks is an old logging town and LaPush is a village on the ocean about 10 miles west of Forks. LaPush gets you into hikes on the Pacific beaches portion of the NP. Depending upon your level of activity you could probably use 2-4 days in Forks/LaPush.
2011 Chevy 2500 Duramax diesel
2019 Timber Ridge 24RLS (Outdoors RV)
Go Cougs!