My daughters and I take the Route 30 at least three days per week to get them to preschool, but this route is so much more. If you happen to live close to NE 55th St, this is a great family route. Here's a sample of some places we have gone:
Magnuson Park - within a short walk you can get to the playground, the kids garden, Arena Sports (jumpy things) and Thistle Theater. If you are hardy, you can get to the water and kite hill. This is a great place to spend the day.
UDistrict - two words: Farmers Market - and it is right on the 30 route, so no walking is involved with those heavy bags. We also love to visit the Burke Museum, several shops on the Ave and a ton of inexpensive local restaurants.
Fremont - we spent one day climbing the troll, touring Theo chocolate, looking at the dinosaurs, eating awesome Thai food and then window shopping while waiting for the bus. This is only just the beginning of all Fremont offers.
Seattle Center - how cool is it to get to the Space Needle, Childrens Museum, Science Center, that huge fountain and a ton of festivals without needing to transfer.
I'm sure I missed a lot, but these are our favorites along the Route 30. We haven't tried much in Wallingford because of that enormous hill between the Route 30 and 45th St, but I think it would work. UVillage is within walking distance of our home, but if you are elsewhere along the Route 30, it would work great to get to all the attractions there too. Enjoy!