the red flag I saw was "drive over to Seattle and down the coast to LA".......with the attention you have given to a
Disneyland lodging choice, I didn't know if you had given that "down the coast to LA" the same attention to the September dates you will eventually choose for Disneyland arrival dates. But then maybe once you choose that Disneyland date you can plan your way back north To Seattle and finalize the as long as it takes. We often have folks who fly into Seattle and wonder about heading south on 101 to Disneyland and come on here asking for advice...so just heads up when you finalize the plan, folks can give you helpful tips here on this site.