As an Open Water Diver going to North FL Panhandle, I think the suggestion of Vortex is good. Water is clear and there's plenty to see for Divers and snorkelers. Swimming/Tubing/Rope swings for others. For the non-cavern/cave types (I'm working on it) there are neat things to do. You can decend down to the cavern entrance in OW and see the reaper sign (don't go past it). There are natural and man made obstacles to swim around. For a first timer, its a lot of fun, after the 5th or 6th run you go less often but its still on the hit list. The folks at the shop are great too, they have almost everything you need and are friendly. I camped there once and had a great time.
If you keep an eye out and depending on the timing of your trip, you may be able to hit Morrison as well, its on the south side of I-10 and has been turned into a park (awaiting various hurdles to open but should be real soon). It has a nice basin, 2 cavern sections to check out, etc. It can end up blown out easily if the river flow is high, but if in town ask around for conditions or just drive over and check it out. Fill up at Vortex and then scout Morrison.
Jackson Blue and Merrit's Mill Pond are really neat, and especially so for trained cavern/cavers. I recently scouted them but didn't dive. You can OW dive the basin of JB, but out of respect for the caving community I decided not to dive OW or push into the cavern. There's plenty of that available when I get a cavern card and worth the return trip and pontoon rental from Cave Adventurers (going to plan a weekend on a pontoon this summer). There's a lot to do there for the trained, maybe not as much for the OW crowd. Its a matter of opinion. Its also worth seeing and there's nice facilities for the entire family at JB, the county has done a great job at the park. Just don't do anything beyond your limits which would be bad for all those who have worked so hard to keep sites like those open.
If hitting Pensacola or Panama City there are tons of saltwater wrecks to see, a day's notice will get you onto a boat trip to see planes, ships, oil rigs, tanks, and even the Mighty O. There are a few beach dives in the area but the springs will give you something to actually see.
Kids can watch the Koi fish at Vortex and have a blast at the place if its warm enough to swim. I'd recommend it for a first timer.