Much as I adore Seaworld, I'm not sure you'd get the value out of a day pass when you have such a short amount of time at your disposal.
I'd take a look at something that would give you a little more bang for your buck. I'd look at something like the Orlando Eye attractions (the Eye, Sea Life Aquarium, and Madame Tussaud's Wax Museum). Gatorland would also be a great choice, and would be MUCH more cost effective ($20-25 pp versus $80 for SW). An airboat tour, as RabFLmom mentioned, is also a fun alternative.
You could also spend your time well at Disney Springs. Book a mid-day meal at somewhere fun (T-Rex, Rainforest Cafe, Planet Hollywood, or wherever appeals to your group). Do the Characters in Flight balloon ride (tickets for that can often be found on Groupon on the off season.....not sure when your trip is). Visit the Coke Store and meet the Coke Bear (Photopass is there, or you can have the CM snap a pic with your own camera), then share a Tour of the World or a float try on the rooftop bar (around $10 for 16 sample sizes). Have family photos taken at the Photopass studio. Stop at Ghirardelli's and enjoy a free chocolate sample, and enjoy some shopping at all the stores before you head to the airport.
Definitely save SeaWorld for another visit, though....when you can devote a full day (or, preferably 2) to enjoying the park
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