Hi Mr. C,
Sounds like an awesome project requiring stamina, nerves of steel, no flat tires, technical agility, and a little luck.
Here are some things off the top of my head:
Churches are not recording studios. The sweet spot may be far away from where the singers are located. Consider a mike where the best sound is in the room, which could be the far corner.
Rush down to Home Depot and buy up their stock of duct tape.
Your plan is to record 4/5 tracks of sound with your cams? Then mix those 24 sets of 4 tracks on your NLE?
If it were possible, you could save some time and trouble if you were able to do some mixing on site. There are some pretty good audio mixers out there in the $400 to $500 range (or you might be able to rent), with 3-4 mike inputs. After the second or third performance, you would be doing live mixing with ease.
You could run your mikes into the mixer with the mixed audio going out to one cam. If you were to double mike the talent (two mikes left, two right..) you could run direct mike feeds into the remaining 3 or 4 cams, per your present plan. You would need more mikes (rent?), but with double miking you could have it both ways, and potentially save many hours of mxing in the studio later.
It's not like you have a couple weeks to get ready for this! As you are loading your truck, happy holiday thoughts!
REGARDS ... TOM 8)