http://www.parentmap.com/article/kid-friendly-hikes-near-seattle-and-tacoma 

1. Grand Ridge Trail Park 

2. Bellevue Botanical Garden

3. Evans Creek Preserve 

4. Paradise Valley Conservation Area 

5. Billy Frank Jr. Nisqually National Wildlife Refuge

6. Margaret’s Way Trail

7. Centennial Trail 

8. Guemes Mountain 

Also: Carkeet Park, Schmitz Preserve Park, Lakeridge Park

A friend shared this on Facebook and admittedly I’m posting it to save for myself (good succinct info including length, logistics and wildlife) for later, but if you are in the area you will like this to you.
I will say, it’s not just people with kids that might like the shorter easier hikes. 

If you’re not in shape, have bad joints, have chronic fatigue, etc. and shouldn’t do huge hikes doesn’t mean you want to stay inside. 

If I take a stroller I can’t find stroller accessibility info readily but can find wheelchair info that helps! 

“Kid” hikes are great for kids and many others! You just might not care if there’s a junior ranger program.