We always go when Splash Mountain is under rehab so I have no idea how wet you would get on that.
On Kali Rapids you can get soaked through depending on where you sit. In the past year or so they added lockers outside the entrance - they are a little past the entrance on your left. You can use them for 2 hours, then have to pay for the extra time with a credit card. On days we plan to ride the Rapids, we always bring a bag with at least flip flops (sometimes a change of clothes) and will put our shoes and bag in the lockers. I have had times when I have put my feet up on the bar and they have still gotten soaked. But the ride is awesome!