Hi Tim,
Since a lot of our community here is out performing Christmas music, I'll hop in
Your suggestion of a woodwind quartet is a great one. I've heard a number of different choral files prepared just as you're suggesting. It really depends on what helps your members to clearly hear their part. Sometimes that may mean mixing instrument groups - winds and brass perhaps, or even strings. A really nice feature of the software is that you can use the Staff Control button "Staff/Setup" for each staff while the file is playing, and experiment with instrument sounds to see what works.
Sometimes the timbre of an instrument from the same group is too close to give good audio separation of two parts that are close together pitch-wise, so you may want to use instruments that are quite distinct from each other. Part of that distinction will depend on the MIDI playback device (eg. GS Wavetable, Roland Sound Canvas, soundfonts, synth module, etc.) you're using as well, so really your ears listening to the file playing on your system will be your best monitor.
ttfn,
Sherry