Would you be willing to post audio of these patches? I have a birthday coming up, and I haven't decided on the wavedrum or k-pro. But a convincing hang drum voicing would definitely tip the scales.
Actually, the MacBook Pro will accept a stereo input. All you need in some combo that gets you dual mono 1/4" to stereo 1/8 inch. The easiest to find would likely be l/r RCA to stereo 1/8" and then add two RCA female to 1/4" male.