without the bodies of the singers and the audience, the sound at the microphone will be dramatically different. an empty room is full of reflections and echoes. I would think, that because the source problem is a cd, it would be worth the attempt to invert it to remove the unwanted volume. as I understand it, it he doesn't want to remove 100% of the cd's content, only reduce the volume level. I also agree it will most likely not produce the desired results, however, I am the type of person to exhaust all resources before I give up :)

Problem solved
 

I love this forum, I got so many creative ideas!

Going back is not an option as this is a no/low budget recording mostly for pleasure and we already paid for renting a large church when we first did the recording; the kid's home church is small and has terrible acoustics. Honestly the whole issue is not such a big deal after all, the recording does not sound all that bad after a little more tweaking. What I did is I EQd all of the tracks a little, raising higher frequencies on the vocal tracks and both lower and higher frequencies on the guide track. I added a little "studio echo" (Adobe Audition terminology) to all of the vocal tracks and to me it sounds acceptable. As suggested above, I cut a little on the middle freqs (around 1KHz), that took away most of the unwanted part. New file attached.

So now 25 kids will have a CD under their Christmas tree - we made these kids (age 5 to 15) proud of their efforts and motivated them for the future.

Thank you so much everyone! Merry Christmas,