I live just east of Mount Vernon, so I can tell you a bit about the area. I have only lived here for a few years, so I don't know all the resources just yet myself.
First, the Skagit area schools aren't the best in the state (20-40th percentile) but as a homeschooling mom it shouldn't matter too much. There are a few private ($$$) schools that seem to have a good reputation. One is in Mount Vernon and the other is an Adventist I think, located in Burlington.
Soccer is pretty big for us as a family. Mount Vernon has a youth program, as does Sedro Woolley. There is Northwest United Soccer club if you'd like to play for really competitive teams. There is 1 big gym called Riverside in MV that has kids activities, a pool and swim lessons (I go there) and there is also a YMCA. You'll find gymnastics, dance, and karate as well in the area but be prepared to pay as it is expensive. We also play softball and baseball (there are leagues all over) and basketball too. We aren't in to football (ds is too young) or wrestling but there are leagues available.
I think there are lessons for piano and violin. A full list is usually posted at the music store in Burlington called Hugo Helmer. These are usually offered by locals through their home.
Housing...hmm that may be a little tougher. I'd expect an acre with a 2500+ sqft house to run you 300,000 to 400,000. It's all location. It could be more or less. It's been 3 years since we purchased our house so I don't know the market anymore.
Two really helpful resources for Washington residents: Meridian Parent Partnership Program in Bellingham - will pay for hs materials up to $1000 per student and offers classes for p/t students. We are enrolled. The other is Running Start, which is a community college access program that high school students can use to get their Associates for the cost of lab fees and books, no tuition.
If you like hiking, skiing, fishing, etc there are tons of activities and the bay is close to MV. Skagit has a ton of fresh produce in the summer and a food co-op. I don't know about culture differences as I've grown up in the Pacific NW but you'll probably notice a few.
Can't think of too much else at the moment. Hope your move goes well if you relocate!