At the Legoland entrance, I was given a coupon by a woman who's son worked at Wendy's. I can mail you the physical coupon if you want (expires 10/29/13) if you want to PM your address. I didn't need it b/c we already purchased tickets, but the woman looked offended when I told her I didn't need it (she said, "I'm a nice lady! I want to save you money. I don't want anything from you!")
You can buy online too:
Here's the url and code for a free child ticket with adult purchase:
legoland.com/wendys
promo code 13000
You can buy 3 different types of tix- Legoland, Legoland + SeaLife, or Legoland + Waterpark.