Moving UK to Seattle

[WhatCanBrownBearSee]

DH was informed by his company yesterday that they are closing the London office in a few weeks and that he has a choice of redundancy or an all expenses paid move to Seattle (or SF, though we prefer the sound of the former)
Firstly, does anyone have experience of living in the Seattle area? His work would be based in Redmond/Bellevue. I know nothing about the cities, or tbh about USA in general. What sort of questions do we even need to be thinking about?
We have 3 young children, one is undergoing treatment for cancer. That treatment is well underway and the company medical will cover it (to our surprise). How do we even start with working out moving schools etc. Our eldest would be in Kindergarten, our other children are younger.

We both worry about our parents for different reasons. Neither set particularly elderly but not young either, all are in their 60s. None are well travelled and my parents in particular dislike flying. Our children are the only grandchildren on both sides and are likely to remain so. We don't live close to my parents in the UK but see them every 6-8 weeks. They adore the kids and the kids adore them. They would be devastated if we moved to the other side of the world. They have been an enormous help to us, especially through DS cancer treatment and I'd feel terrible taking their grandchildren away. That said, our parents' feelings can't really be the only deciding factor in making us stay.

Where do we start with making the decision? Redundancy wouldn't be a problem for DH. The package is generous enough and he is in an industry where he is unlikely to struggle to find another role in London. We had assumed that DS medical issues would make moving impossible (and tbh almost hoped that they would so we wouldn't have to make a decision)
Although we don't know a lot about the area, DH colleagues suggest that the quality of living could be much greater out there. We've had a turbulent few years and a place with a slower pace of life would be lovely. But that could just be sugar-coating the Unknown.

Does anyone have any thoughts, experience of moving away from the familiar, ideas about the location or anything else we haven't even thought of yet please? My gut reaction is to stay put here, but there's a certain pull to the change that means I don't want to dismiss it out of hand just yet.

[cheeseismydownfall]

First off, is this a temporary or, the sounds of it, a permanent move? What visa are they proposing? That will help people to advise you.

for your DC.