While Kona Village Resort and Four Seasons Hualalai both offer some nice beaches of their own, there are some other very nice options nearby. One of those is Kua Bay, which is part of Kekaha Kai State Park. Due to it being part of a state park it offers lifeguards as well as restrooms.
Kua Bay is roughly 1 mile south of Hualalai Resort. As you exit the highway you will take a paved road roughly a mile towards the ocean. There are a few parking stalls as well as a few handicap stalls. All the rest of the parking is located on the side of the road. Near the parking are the restrooms. Shortly down from that are outdoor showers as well as some picnic tables. As you travel down from that you will reach the beach.
Kua Bay is a nice white sand beach and is located on a bay so that typically means the waters are relatively calm. In the winter months there can be some waves that are great from children and boogie boarding. There are several reef areas off of the beach that offer great snorkeling.
There is one thing that Kua Bay does not have and that is shade. Due to this, you will want to make sure to bring a beach umbrella. It does fill up fast so if you want a nice spot or have a larger family it is recommended to get there before 9 am.
Kua Bay used to be one of the hidden treasures on the Big Island of Hawaii, but once they made the nice paved road to access it it became one of the more popular beaches on the Big Island.