Sea Tac to Forks about 3 &1/2 hours in your rental car. Sea Tac to Paradise/Mt. Rainer 2 hrs. Forks to Rainier 5 hrs. Alpine regions in both Cascade and Olympics still have snow until mid July usually. Get a tide table for walking west coast beaches. Those not wanting to hike the Wilderness Beaches of the OP should bring ice axes, crampons and snow camping equipment for their early season alpine expedition.