From my somewhat limited experience recording all-girl a cappella groups . . . and given your relatively small funds and resources and what not . . .
I would recommend recording the entire ensemble in one room, minus the soloists . . . or at least have the soloists shut up rather than sing.

Station the vocal percussionists several feet away and out of the mic's range from the rest of the ensemble -- but still close enough so they can be heard by the rest of the group.
You could also try putting them in a separate room, but then you would need to invest more money in head phones, cords, etc. etc. so that everyone would be able to monitor them over the headphones while you perform.
My favorite method for recording the ensemble would be to have them all get in a circle around a stereo pair of condensers. You could probably get by with a pair of Oktava MC012's from Guitar Center. Tell the butt monkey working the counter that it's for a non-profit organization, so you'd like to see if they'll give them to you for a $100 for the pair.
You could also do the same thing with the vocal percussionists. Have them get in a mini circle around a pair of condensers. You're probably going to want to stick a pop filter over their mics and have them get in close -- almost right up on them.
You could then have the soloists overdub their parts after everything else has been tracked. For that, I'd recommend picking up
a CAD M179.
http://www.frontendaudio.com/CAD M179.htm An outstanding mic for female vocals, and it's very cheap.
All told, these mics will set you back about $400 for the lot. That's about the rock-bottom price I'd be willing to shell out for decent mics. You're obviously going to need to raise more dough for the rest of the stuff you're going to need.
For that I'd recommend throwing a kegger. 
Preferably the kind with lots of beer and hot women running around.

he he. Just kidding. You might consider approaching your school's student governmental body -- student council or Board of Ed if you're in High School or student senate if it's university. You could have a bake sale at a game, host a dance, any number of things. Use your imagination.
Here's some stuff I recorded for the University of Chicago women's aca pella group,
Men in Drag :
http://www.nowhereradio.com/artists/album.php?aid=1298&alid=402
Good luck