Town Park is a lovely spot to take a break. Enjoy a picnic lunch, throw a Frisbee around or just lie on the soft grass and close your eyes for a while.
You'll have no end of sightseeing choices when staying in Kapaa. Town Park is a good place to kick off here, but there are plenty of other worthwhile attractions to appreciate. Lydgate Beach, Coconut Marketplace, and Wailua Falls are near the recreation and green space and will top off your day nicely.