Hi there,
I'm from Austin and now live in Plano and SA is a great spot that we love to vacation. When we do Sea World, we always stay at the Westin La Cantera Resort. It's more on the $$$$ side, but totally worth it! I will say, we found several deals online and my mom heard one on the Austin radio one year about an all-inclusive 3 night package with tickets to Sea World or Fiesta Texas. We did that, but it's been maybe 7 yrs? There are many other hotels in the area. Once, we tried the Radisson, and it was ok and more on the $$ side, but I prefer The Westin (of course).
I don't know how old your kids are, but I'd encourage you to take more than 1 day to do it. When you pack it in to 1 day, everyone is tired and overheated and grumpy and miserable. In 2 days, you can plan your breaks and enjoy the park more. There really is a lot to see and my kids love it.
Have fun!!