Are you mostly recording close to the sound source? An omni mic like the CAFS is great for that; not so great if you'll be further back. For that you need something more directional like the CA-11 cardiod.
That said, I find that in the realm of very inexpensive small mics, the small omnis sound much better... You might also look into the Church CA-1, which are quite small and recently held up well in a head-to-head comparison with much more expensive small DPA microphones.
Point being, if you're stealth taping, my personal preference is, get close or don't bother; therefore, go with the small omnis like you suggest. But there are plenty of folks who routinely stealth tape in stadiums, amphitheaters, whatever... and they'll tell you to get the CA-11s.
You also need a power supply aka "battery box". The M10 supplies enough voltage to power some but not all mics; I'd not risk it and get a battery box, personally. Church Audio makes the cheapest one, the "CA-UBB" which I think is $29. For a bit more, the boxes from soundprofessionals.com like the SPSB-8 are a bit sturdier (full case around the battery). I prefer the SPSB-10, which is tiny, but it does use a more expensive and harder to find battery.