We are Argentinian, and we are moving to Seattle on December 2019. Do you know private or public elementary schools with dual immersion programme (spanish-english).
Here are a few schools that might suit your needs. All are public schools offering English/Spanish dual-language immersion programmes.
Also make sure you check out our page on Education and Schools in Seattle for an overview of the schooling system. Bear in mind that public school attendance is regulated by catchment zones, so it's best to make sure you move to the zoning area of your desired school.
Best of luck with the move.