I also posted in the CL thread but I will expand a little here.
My 1.5 year old son loved the little kid Splash park. Your 6 year old may be a little old for it, but I think your 4 year old will like it.
They have lawn games set up in the late afternoon/early evening. Like, hula hoops, bags, giant checkers & connect 4, etc. My son just liked picking up the stuff and looking at it, but your kids could probably actually play the games lol.
He also liked sitting in the rocking chairs in front of the fireplace and walking over the bridge in the lobby.
The boat ride to and from the MK was a real hit for him.
They have coloring pages/crayons in the CL lounge, which your kids can probably use better than mine...he just scribbles right now. They have kid-sized tables and chairs in there too. My son still needs a lot of help eating, but your kids could probably make a "kids table" if they want!
WL is a fabulous resort for young families and I'm so glad we chose it for our first vacation as a family of 3!