You're on the right track. The MCE 94 mics will do a fine job on the acoustic guitars. Start with each mic positioned about six inches from the guitar, pointing at an area between the soundhole and where then neck joins the body. Moving the mic closer to the soundhole will warm up the sound (often boomy), and moving down the neck will thin out the sound. Try moving closer (i.e. 2-3" off the strings) for better separation and room rejection.
The AT2020 is your best bet for vocals. Try setting it just beneath chin level and pointing it up slightly. If the vocalist sings over the mic, you shouldn't need a visually-distracting pop filter. This positioning will also give you better separation if the vocalist is also playing guitar. Keep the mic within a few inches of the mouth for better room rejection.
I mentioned "room rejection" twice now because, frankly, you don't want the room to be a part of this recording. No small apartment has good acoustics, so your best bet is to try to suppress as much room sound as possible. You can then add some ambience back at the mix stage (i.e. a small chamber) to sweeten the sound in a subtle, realistic way.
If the Zoom can record five channels, use it in stereo for the room sound and audience reactions. Point it at the musicians from a few feet away if you want that perspective to add to your mix. You'll get lots of room ambience and early reflections, which may not sound great because of the small room. If you want audience reactions only, point it away from the musicians and back toward the audience. Mix that back in between songs.
If you can get set up 30 minutes before the show, run some test recordings and refine your mic placement. You could show up and record this without any prep, but your results will be better if you have some time to dial things in.
