Island Lake County Park is a sweet little park tucked into a forested area between Poulsbo and Silverdale. There is a wide, paved trail that meanders near the lake, spanning the length of the lake from one end of the park to another.
Hiking the entire trail system will likely take just a couple hours, and along the way, you will see people fishing from access points, a swimming beach, and plenty of picnic areas. It's a wonderful place to spend an afternoon.
Beginning from the northern trailhead, you can take advantage of the restrooms before heading out along either the paved trail, or there is also a forested trail that you can take to wander through the woods as an alternate route.
Pass a swimming beach (lifejacket loans are just a little further down the trail if you need them). Otherwise families can play here for a while in the sand - it's a great beach for kids.
Continuing on the paved route, pass a fishing spot before ending at a second parking area at the west end of the park. There are no restrooms at this end, though you will likely find places for a picnic or benches for a rest before you turn around and head back the way you came.
WTA Pro Tip: Expect to share the trail with horses and bikes here, in addition to non-motorized boats. The community center at Island Lake is also available for rent. Details here.