With the ages of your kiddos, I think it's a good idea to get each bird from a different breed, so they're easy to tell apart. I have a hard time telling one barred Rock from another

, so make it easy on the littles.
If you get Easter eggers, chances are good they'll look different when they're grown, so they'll be easy to tell apart. Plus, they'll lay different colored eggs, not just blue. I think your mix sounds good. You'll have light and dark brown and shades of blue or green, it will make a nice basket. And all those breeds would do fine together.
Living in wet/rainy Oregon myself (not as much as you, but still), I've found you can keep pretty much any breed with our climate. The only problem I've had is feathered feet, they tend to ball up mud and they lose feathers in the winter, not the pretty fluff you see in other folk's pics.