Dewey Park in Johnston has a large playground with three play structures. There's a large open field, a 1/2 mile paved trail that loops around the park and a Little Free Library. The only thing I didn't like about the trail is that part of goes right through the center of the parking lot, which is definitely not safe for little kids on bikes or scooters.
Play Structure: Ages 2-5 & 5-12 (separate areas)
Surface: rubber chips (ages 2-5), wood chips (ages 5-12)
Swings: traditional, toddler, plastic tire
Restrooms: seasonal modern restrooms, portable available in the winter
Parking: large parking lot