Thanks. What's a good, budget mic that could work for this application?
The Mackie desk might solve your short term problem of no mic pre-amps but it might be wasted money as when you want to step up in quality, the Mackie will be one of the first items in your chuck-out list. Given the choice, I would look at a ProTools M-Powered or LE system, instead of the Mackie. You'll get more ins/outs, integral Mic-pres and industry standard editing and mixing software, although the software does take a bit of learning.
Electronic drums are probably your best bet at this stage. Easiest way to do this would be to get a software drum module and then a MIDI controller or just program the drums in software if you don't need the hands on performance with sticks. There are some decent drum modules available if you get say Cubase or Logic (or ProTools). The upside is you won't need any more mics or inputs, the downside is that you won't get the experience of recording or processing live drums, which is an art in itself.