Five accesses, three towns, and one of them is not on the Gulf at all.
John Beasley Park, Okaloosa Island. The county's flagship: a large free car park, covered pavilions, restrooms, outdoor showers and lifeguards through the warm season, next door to the visitor centre. The best default for a family beach day, and the easiest to explain to somebody who has never been.
The Boardwalk, Okaloosa Island. Officially Newman C. Brackin Wayside Park. Free parking again, plus shops, casual seafood and bars around the base of the pier, with pavilions, volleyball and a playground. Busier and noisier than Beasley; better if you want lunch without moving the car.
Okaloosa Island Pier. The walk-on structure runs 1,262 feet into the Gulf. The current pier dates from 1998, after a storm took the 1972 one. A small fee to walk, more to fish, and the best free-standing wildlife viewing in town.
Okaloosa Day Use Area, Gulf Islands National Seashore. On the bay side of the island, open from eight to sunset, with a small-craft launch, restrooms, showers and picnic tables. Entrance fee per vehicle, valid a week across the seashore. No overnight parking.
Liza Jackson Park, mainland. Not a Gulf beach: a sound-side city park with over a thousand feet of frontage, a fishing pier, two-lane boat ramp, playgrounds and a dog park. The local answer to a hot afternoon with small children and no intention of driving.
James Lee Park and Henderson Beach State Park are both in Destin. Good, and a drive.