ok, been to Seaworld orlando today.
used the 20% southwest discount.
at the end of the day, went to the window at the exit, and did 2 things:
1. upgraded the tickets to include aquatica for 25$ per person
2. they asked if i wanted the second day for seaworld (i said : no)
on the tickets purchased at the gate there is no mentioning of the price you paid or that it's discounted.
i think that if you want seaworld+aquatica (and not for 14 days like on the online pre-purchase) you can do the trick i mentioned above.
the tickets for aquatica are good to be used within 1 year