Multi track recorder from a mixer and laptop, How would I do this?

I have been elected as the audio engineer of our schools music appreciation club. We have a Crate PCM-8+. Its a mixer and mono amp. So the idea would be to hook my MacBook up to it so that its a multi track recorder of sorts. I was thinking of using the RCA out and in for the tape deck, and hook those up to the internal sound card on my mac. I just need advice on whether or not this is a good idea. I would also like some suggestions on recording in general.