I can't answer your question about the Wendy's discount code, but I can tell you about a discount that I used when we visited in June.
If you go to the Southwest Airlines website - www.southwest.com - sign up for their Rapid Rewards card. They will send you a card in the mail, but you can also print a temporary card just after you sign up. Take the card (or the printed copy) to Sea World, and that will give you a 20% discount off tickets.
The main drawback - for me at least - was that you had to wait until you got to Sea World in person and buy tickets at the gate.
But from what I have seen, this is one of the best discounts off Sea World tickets.