My choice of name would be "Splash Bayou." It retains the "Splash" of the original and replaces one geographical feature with another. Using the word "mountain" would just feel so out of place for an attraction whose location in the swamps of New Orleans is so integral to its character (I know there are no mountains in SotS either, but Chickapin Hill is close enough, and the ride's general location isn't all that important anyway). It could still maintain "Disney mountain" status without "mountain" in the name, the same way the Matterhorn, EE, and 7DMT do.
Knowing Disney marketing, they'd have to append the obligatory subtitle, so something like "Splash Bayou: Tiana's Mardi Gras Adventure"