Hi Scott,
congrats on your new Mackie's. I think you made an great choice.
They are on my current wish list too.
Way back when, I bought a small Mackie Mixer, VLZ1202. Great little think for the money. That would take care of your problem.
The reason why I had to add it to my powered speakers (still JBL Eon power 15), was that I had to run two mics through it (my wife and mine).
The Mackies sound really great. I had the chance to test them a few times.

Good luck, have fun

Eric