I think the Flex Ticket only lets you get in one of the 5 parks at one time. If u decide to go to Sea World and Universal the same day, u can do it, but after that your ticket will only be good for the other 3 parks. The Flex Ticket only lasts for 14 days, after that it expires. It doesn't mean that for 14 days u can go to all this parks whenever u want. I suggest you only go one park each day, so u can appreciate more what each park has to offer.