Coming from a local of Destin/30a this is what I do visiting the area.
If I were visiting Destin my first matter of business would be to wake up early go for a long peaceful walk on
Okaloosa Island, hunt for shells before they are picked through while enjoying the beach and the serenity when it's practically empty. The next thing I'd do is go grab breakfast and coffee at beach view. Beachview is an awesome little spot that serves brunch type food, coffee and drinks right on the water on Okaloosa island, which is right next to Destin. Next I'd head towards historical downtown Fort Walton Beach, I'd check out the Indian mound then go across the street to Fluid surf shop and the landing park. When at Fluid I'd ask about renting a surf board and look at their super cute beachy apparel. Next I'd go to the pier on Okaloosa Island, walk it and look for turtles and dolphins. While there I'd check out the Gulfarium next door and watch the dolphin & seal shows, and check out all the animals there. If you are coming with kids you definitely need to check out the water park Big Kahuana's it's so fun. For dinner you have to check out Dewey Destin, it's an awesome seafood restaurant, I always order the bacon wrapped shrimp. If you're looking for good coffee in Destin definitely head to Maas coffee, I like to order the redneck latte it's a white chocolate vanilla latte that's sprinkled with cinnamon.
When coming to Destin you have to go to Mgguires Irish Pub, their pork chops glazed with Irish whiskey is to die for and you'll have to grab an Irish wake drink. If you're coming to Destin you have to check out the Harborwalk marina for lunch and dinner there's a ton of restaurants and fun things to do for kids such as zipping and bungee trampolines. While there you'll see hundreds of boats in the marina many bringing in their catches for the day from deep sea fishing. On Thursdays the harbor walk has a really cool firework show, it's neat watching it over the marina. One of the staple things I'd do is rent a pontoon and spend the day at crab Island, it's so neat feeling the salty air and exploring. Lastly and obviously one of the things you'll want to do before you even get to the area is book a photo session to capture your amazing vacation and memories, you won't regret it. Hope you have a great trip and bring lots of reef safe sunscreen.