Kohanaiki Park, just north of Kailua Kona, is a popular park which provides a great view of the sunsets, has a good surf break, has protected pools for keiki to paddle in, and has all the facilities needed for a good barbecue.
If there’s a downside to the park, it’s that it’s just south of the airport. It’s not O’Hare, but planes come and go with some regularity. It’s also used by the military and planes, such as this big C-17 transport, practice touch-and-goes with some frequency. So it’s not the most relaxing beach on the island, that’s for sure, but with white sand, blue water, and hot sunshine, it has a lot going for it.