Soundbridge

"A fun musical experience"

My kids and I recently visited Soundbridge for the first time and had a lot of fun. Soundbridge is located at Benaroya Hall in downtown Seattle, and it's an interactive music experience for your kids.
Soundbridge is located in a fairly small area, but it's stuffed full of instruments and toys and musical activities for your kids to take part in.  There's even a Wii set up with some fun music games.  
The staff is incredibly friendly and happy to demonstrate any instrument that your child is interested in- while we were there we played with the guitar and drums and the cello.  
On Fridays Soundbridge is free after noon, and they have a free musical storytime at 1:30 on Fridays. At other times admission is $7 for adults and free for kids under 5.  They also have lots of other classes going on there through the week like Kindermusik and Discover Music classes.
If you want to introduce your kids to music or if you already have a music lover on your hands, I'd suggest a trip to Soundbridge to see all they have to offer!