There are quite a few people who can do it in one day. You’ll also have to consider how long you’ll be able to stay out in the heat in June. You may even consider a 2day combo ticket and spend half of each day at Sea World and the other half cooling off at Aquatica depending on what your other plans are.
We went in October. It was 84 degrees on the first day but with significant breaks out of the sun and taking the time to get inside for some AC, we did stay all day that day. My crew goes nowhere fast, so I scheduled 2.5 days so we could see everything and repeat certain parts of the park if desired. We ended up doing 2 full days, repeating the Whale show, missing the Pets Ahoy show.
I will say though I had an 8 year-old and a toddler and we didn’t do thrill rides either, but we spent a significant amount of time in Happy Harbor, which may not appeal to your ten year-old son. Although he may enjoy the splash area in Happy Harbor since it will be hot out. There are some trip reports on here. I have a trip report further down the page called “Visiting the Fishies…” if you care to read how we spent our time there.
