Not from the area and don't have anyone in our group with disabilities but is this a good option for a couple of young families to take small kids to enjoy some water activities (splash pads, etc) as well as other activities? Mainly as a an alternative to Sea World or Schlitterbahn since the kids are a little young to get the cost benefit with that.

Yes. We've done it with our 2 y/o several times. He loves the trains and all of the interactive stuff. We've always gone early to avoid the crowds.