Washington Trails Association is my go to site when I'm in the mood to find a great hike.

Recently, they featured "Hikes Close to Home" that help you find a park, trail, or greenspace near you.  Just because.

Some kid friendly hikes:

Coal Creek Falls

Franklin Falls-Snoqualime Pass

Boulder River Waterfall-Arlington

Ebey Landing-Whidbey Island

www.wta.org