If you want to do Karaoke properly, take a look at something like this:
https://www.bax-shop.co.uk/digital-m...-xr12-mix-rack
It comes with processing on each channel - meaning you can properly eq, compress and reverb each channel (each mic)
You'll find the gate and compression will really help with levelling out each singer's volume.
For the price, and the functionality, it's a bargain.
And to contradict Excalibur, I'd run the MC6000 in to the live mixer, and take your feed from the live mixer in to your amp/speakers.