+1 on Machineguns America
https://machinegunamericaorlando.com/I have never been there myself but people have told me they had a good (but expensive) time.
For SCUBA, many Dive shops can offer you a "SCUBA experience" that gets you in the water on a shallow water dive the same day. This isn't really the time of year for it (the water is a little too cool for my taste) but I am sure somebody is offering it. Call well ahead to inquire and make reservations. Not really a walk-in type thing unless all you want to do is dive in a pool. You'll have better luck in the Keys.
This is a good time of year to visit one of the many Springs and rent a canoe. The weather is not too hot and you have a good chance of seeing some manatees. If you are in Orlando, I recommend Blue Springs State Park
https://www.floridastateparks.org/parks-and-trails/blue-spring-state-park/manatees-blue-spring-state-parkKennedy Space Center is a good visit. Make sure to find out their operating status during COVID. Fun Fact; I helped build the Space Station Processing Facility
Lots of places to rent a canoe and paddle. This time of year you will often see BIG Gators sunning themselves during the day. Cracker Creek is nice
http://www.portorange.com/resources/cracker-creek.htmlbut Wekiva Springs is closer to Orlando https://www.floridastateparks.org/parks-and-trails/wekiwa-springs-state-park/experiences-amenities-0
Don't discount the many nature trails/parks in and around Orlando. Good time of year to do outdoor stuff in Florida.
Disney Springs is a free to enter, more mature shopping and dining complex https://www.disneysprings.com/
City Walk at Universal is a similar venue.
St. Augustine is a bit of a drive from Orlando but well worth a day to visit if you have the time.
For a day at the beach, I recommend the beach at Ponce Inlet just south of Daytona. More of a locals beach, less crowded and more things to see and do.