Circle Seattle
 

9/22 Arrv SEA TAC; to San Juan Islands & Olympic NP. ISO whales & eagles.
One day & nite Seattle, 9/29 Dprt SEA TAC.
Rental Car- full drive or mix it up w\ ferry? how or at which pts?
Any lodging recommends welcome.
Is it too ridiculous to include Mount St Helens in this loop?
TYIA

Please say if I am understanding correctly... in 7 days you want to spend 1 day in Seattle (plus you'd need to be back to fly out the last day) so you have 5 days left to see the San Juan Islands and Olympic National Park and include a whale watching cruise? That's simply not enough time.

Yes you need a rental car for all of this (except maybe your first and last day in Seattle). No you definitely do not have time to go all the way down to Mt St Helen! :-)

It's doable if you don't mind moving at a very (very) high pace. You can see whales from the San Juans or you can see them from Port Townsend or Port Angeles on the Olympic Peninsula, and in fact I would suggest the latter in order to conserve some time. As for eagles, they fly around and you might or might not see any (you probably will but this isn't an open-air zoo, y'know.) If you're not desperate to see the San Juans, and wouldn't mind substituting wonderful Whidbey Island instead, you'd have an easier time of things logistically.

One of the key attractions in Olympic NP, the Hoh rain forest, will be inaccessible from the middle of September through mid-October (at least) as the road into the valley is being reconstructed. You can visit Hurricane Ridge or any of the coastal strip's beaches, and the Quinault rain forest will still be open, but that's a very long drive from the other parts of the park. Two days for whales and Whidbey, and three for the Olympic peninsula, and you're good.

Mt. St. Helens is over three (boring) hours from Seattle each way and in late September the odds are high that all you'd see is clouds anyway. Skip it.