Sea World hosts the Spooktacular weekends in Oct. Trick or treating usually starts around 12. There are special shows and extra characters. Face Painting, make a tee and dance parties. All included in the regular price of admission.
It's Shamu's Spooktacular, it's not scary and it's a blast. Best of all, it's all month long and included with regular park admission. Costumes are not required, but still part of the fun. Read an FAQ and see pics here.