The easiest option is to get a pre-amp with as many channels as you need, and you can mix the mic's on the pre-amp and send that signal to the Powerbook as one stereo channel so you can mass mix the whole kit that way and add effects through whatever software you're using.
It must be noted that a high quality preamp is of the utmost importance when recording percussion (or anything else for that matter). Different preamps will change the sound of a microphone exponentially. Here are some preamps that I have found useful for recording Drums and Percussion. I have included their characteristic sound after each model.
- Millennia Media HV3B -- Transparent and fast
- Grace 101 or 802 -- Transparent and fast
- Neve 1272 -- Very Colored
- Telefunken V76 -- Very colored
- Great River MP3V -- Colored or transparent
- API - All models -- Colored
- Manley -- Slightly Colored
You might want to start with an uncolored pre and try to get your sound with the microphone first. Then, if desired, you can change the pre to give the mic a different personality. Some micís such as the Sennheiser MKH series and the B&Kís are very transparent and accurate. These micís tend to work great with a colored pre.