The water parks are really great and if you have never been to one, do it, assuming you have water-lovers in the family. The theming of both TL and BB is very cool. We like the BB slides best but the TL wave pool is awesome enough to draw us back there, as well.
Many years ago, when just DH and I travelled to WDW, we would never be staying close enough for a midday return to our resort. We would head to TL, cool off in the water and nap in the shade for a bit, then clean up and head back to a park for dinner and evening fun. Now when we travel with our intensely aquatic DGSs, time spent in the water parks is every bit as important as the theme parks. Our older DGS made his first visit to Ketchakiddie Creek at 8 months, and absolutely loved it. Now it is all about body surfing the big waves and racing around to the slides.
If you are adding Water Parks and More to your passes, and the season permits, try both TL and BB. They make a fantastic change of pace.