[nicfit]

Well, if you DON'T need to have each instrument on a separate track (in which case you'd have to carefully place some decent mics, choosing beetween models that can "capture" nicely the sound of each instrument, use some sort of external soundcard to record the separate tracks, mix a bit the sounds before feeding it to the card or mixing/editing each track on the mac afterwards)
AND you go for the "all in one" recorder you'll record straight to the memory card on the device, then transfer the file(s) to the laptop, basically...still a bit of editing can be done, if you're going for improvised stuff a handeld thing could be a cheap-ish (assuming you'll split costs) way to start getting things recorded, if you're happy with the results just stop there, if you'll feel the need for an upgrade a decent, smallish (motu ultralite?) card + a mixer could work nicely combined with a bunch of mics. Price would be obviously higer...