A couple more considerations:
I would not want to rent out my primary home as a vacation rental because removing/storing/locking all personal items, clothing, paperwork, valuables, pantry items, etc. would be too much of a hassle. Try it once before going on vacation, and list your home for rental for your planned vacation period only to see if it's worth it to you. (You could try listing your home on HomeExchange.com, for lower-expectation travelers than the ones who are paying actual cash and then reviewing your property).
A long-term caution: if your retirement financial security depends on renting out your primary home for a good part of the year, what happens if one of you has an illness or injury where you would want to be in your primary home, near your doctors and community, for a year or two without interruption?
A plus to your plan, tax-wise, I think (though I'm not an accountant), is that you might be able to write off travel from your primary residence (Seattle) to the secondary one (eg Hawaii) against rent revenue as trips to manage the property, assuming you will do chores, repairs, purchasing, meeting with property managers, etc. when you are in Hawaii.
Also, I think someone suggested that the taxes you collect are deducted from the rents you receive, but, at least in my town, the substantial local hotel taxes are charged to the traveller, on top of the rent, and I collect and remit them on a monthly basis to the city and state (losing a bit, because they are paid with a credit card, so I receive 97% of the taxes, but then pay 100% of the taxes with a check).