There are some new trails to explore in Whatcom County and some that need to be rediscovered. I haven't had to check these out but they look like great beginner trails though rock trail has stairs/ladders.
StoryWalk Trail in Lynden starts at Million Smiles Playground Park. This is a favorite park of my children. The StoryWalk Trail is a trail that existed before in the park but now has a laminated story, Totem Tale, that folks can read as they walk the trail. It has a grand opening so to speak on Saturday the 17th.
Nooksack Loop Trail portion is now open in Ferndale. This is the first segment of the Nooksack Loop Trail that is open. You can now walk the Hovander River Walk through Hovander Park and see the official trail markers. It also officially opens on May 17th also. Here are some more details.
Rock Trail is the newest addition to Larrabee State park. It can be accessed from the Cyprus Gate Overlook. Rock trail is a connector trail to Lost Lake. There is quite a lot of interesting geology to look at on this trail read more about that at NW Geology Field Trips. A trip report can be found here by Todd Elsworth from the Be in Bellingham blog.