I could not be more thrilled for your kid, and by extension you, that everything clicked at Washington. It was quite the journey but you had a really thoughtful process, and it paid off.
For the record, I agree Washington has a crazy-nice campus in a great setting in a great city. It has also long been one of the most important research universities in the US in a variety of fields. So I am honestly surprised it is not more flooded with applications. I mean, I guess it is for things like CS, but it seems like a reasonable target for a lot of other majors, even OOS.
Anyway, congratulations on a great process and great result.